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No. 8 July 2007
COUNTERFEITING SNIPPETS FROM AROUND THE WORLD
Examination of two counterfeit coins [denarii] from the [Birnie] hoard 1
"Counterfeit coin of the realm - Review and case study analysis"
The Infamous Ashmore Coins: Anglo-Saxon Pennies: Volume I
This newsletter has now been in production for four years. In that time it has attempted to avoid too much navel gazing, as this can be boring for the reader. However this seems an appropriate time to review whether it is performing a useful function, whether it can be improved and whether its menu of brief news items, features and reviews etc. should be changed. The editor would welcome views from readers on which items they find interesting, which boring or unintelligible and whether any new areas should be covered. As an example, an email in the early days of this newsletter from Mike Marotta pointing out the difficulty of reading the site with its previous dark background was useful and much appreciated.
Firstly some facts about this site, the whole site now has between 1,500 to 2,500 visitors a week. The majority of these hits are to one of the various editions of this newsletter. Most visitors do not stay long but a consistent ten to twenty percent spend a significant time visiting the site. This is not a large number compared to some websites but then coins and specifically counterfeit coins are a minority interest. The geographical spread of the visitors is vast. In just this last week the visitors were from forty-seven different countries. The main weakness is the scarcity of visitors from South America, presumably is due to language, and Africa, presumably due to poverty.
The most important sites referring visitors are Google and Google Images with the other major search engines such as Yahoo and MSN a long way behind. Other consistent referrers with small but steady numbers are Wikipedia and sites such as Reid Goldborough's counterfeit coin site, Predecimal and CoinLink. Finally every so often the site has a surge of visitors from a blog or a chat room. Sometimes this is from a coin-interest site such a Coin People or Coin Talk but often it is a non-coin site. One such chat room that recently generated hundreds of visits was a Portsmouth soccer fan club.
Apart from the numbers of visitors how does one judge the success of a website? The editor considers it is mainly from the judgement of the coin fraternity. So a profile in the British magazine "Coin News" with warm words about the site was welcome. Also references to the site in two recent scientific papers were much valued by the old scientist in the editor. Perhaps the finest(?) accolade was on Coin Talk, "should have realised that such a great work could only be done by a fellow Welshman, ... very interesting read", De Orc.NEWS
Respected Celtic coin specialist dealer, Chris Rudd, has posted on the news section of his website details of fake trophy type gold quarter staters that are currently circulating. He has posted photographs of five examples of these counterfeits and details of Celtic coin expert, Dr. Philip de Jersey's opinion of these coins.
Dr. de Jersey is quoted as saying, "A number of near-identical trophy type quarter staters have appeared on the market in recent months. All are from the same pair of dies and I am sure that they are modern forgeries." Among the points made by Dr. de Jersey are:
1. Although these coins are struck they have no die links to any genuine pieces.
2.These coins have uncharacteristic smoothness to the edge of the flan compared with all the fifty or so known genuine example that generally have ragged flans with edge cracks.
3. The examples examined in hand by Dr. de Jersey were made from a yellowish gold instead of the expected coppery gold.
4. None of the suspected counterfeits have a secure findspot - no metal detectorist has reported a find of a coin of this type.
Chris Rudd should be congratulated on publicizing details of these fakes. Certainly, if the editor collected Celtic coins Chris Rudd's actions would be a recommendation to deal with him. It again must be emphasised that compared with areas such as Roman and Greek coins Celtic coins are not often counterfeited.
[Source: Chris Rudd's website www.celticcoins.com]
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The counterfeit one-pound coin recently identified by Alan Humphries. Click on the counterfeit to see an improved image.
Die cracks on a 2005 one-pound counterfeit
In 2004 the United Kingdom started on a new series of annual one-pound coin designs based on famous bridges; one for each of its four constituent countries. Unfortunately the new designs included replacing the edge lettering introduced with the first one-pound coin in 1983. Up to this time a fault in the edge lettering was one of the easiest methods for detecting a struck brass one-pound counterfeit coin. The Royal Mint described the new edge design as an "incuse decorative feature symbolising bridges & pathways".
In the last Counterfeit Coin Newsletter it was reported that collector Alan Humphries had found counterfeits of the 2004 and 2005 Bridge series one-pound coins. Alan now reports he was recently given a fake 2006 Egyptian Bridge reverse coin in his change. The editor has fully examined six twenty-first century counterfeit coins including one 2005 "Bridge" counterfeit. The full results from these examinations will shortly be posted as one of the poundfiles pages on this site. From these results and Alan's and another correspondent's observations some tentative advice can be made about detecting some of the current "Bridge" counterfeits.
The evidence suggests that some of the Bridge series counterfeits are significantly different in a number of ways from the type NP counterfeits. The editor had previously classified these NP type pieces as the predominant struck brass counterfeits. The differences include use of a different brass alloy, use of a coin die with a very "rough" surface and the frequency of die cracks found on the counterfeit coin. It is not possible to know whether this means the counterfeits are manufactured by a different organisation or the organisation previously considered the most important has just change some of it manufacturing processes.
Incuse edge lines misaligned at one of the two breaks on a 2005 counterfeit
Missing millings on a 2006 counterfeit
Identifying some of the Bridge series counterfeits
The texture of the surface is often the most obvious sign if a coin from this series is a counterfeit. The counterfeit surface has a dull, matte finish as if made from a spark-eroded die that had not been polished. Under an eyeglass or microscope the surface can be seen to be very granular and uneven. Also often found on the coin faces are a number of small raised meandering lines. These are caused by cracks in the surface of the coining die.
The quality of the edge on these counterfeits varies from the superficially good to poor. In at least two counterfeits the incuse lines of the edge design were "misaligned at one of the two breaks". Also found were horizontal breaks in the millings giving a "chequerboard appearance" and missing millings
[Sources: A.Humphries, an anonymous collector of Roman coins known to the editor and the editor]
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This photograph shows an Australian 1917 sovereign that has had its mintmark removed. It purports to be a very rare 1917 London minted coin. The mintmark should be on the ground above the gap between the 9 and the second 1. This coin was sold in an Internet auction about two years ago.
The USA Mint recently made a mistake issuing a number, perhaps running into the thousands, of its 2007 Presidential dollars coins without edge lettering. This edge lettering includes the renowned, “In God We Trust”, motto. This news was soon followed by a warning from the PNG, Professional Numismatists Guild, that edge lettering was being removed from normal dollar coins and these altered coins sold to unsuspecting members of the public.
Although not given as much attention as completely falsely made counterfeit coin, altered coins are often a significant hazard to the collectors of milled coinage. These alterations can occur in many forms. Two of the most common methods encountered by the editor are altering the numeral in a date or removing or adding a mintmark. The majority of the alterations seen by the editor can easily be spotted under a powerful eyeglass or a microscope.
Perhaps one of the most well known British altered coins surfaced in the late 1960s/early 1970s. This was a supposed 1933, George V, penny. According to Freeman ["The Bronze Coinage of Great Britain", reprinted 2006] only seven coins of this type are known with just two in private collections. A 1972 published paper, note 1, explained the scientific examination of this coin. Previously the Royal Mint had concluded by simple comparison with a genuine coin that the final digit in the date was not correct. The authors of the paper considered that the counterfeiter had removed the correct digit and soldered onto the coin a three that had been removed from another coin.
Note 1: "A microscopic examination of an alleged 1933 penny", L. Green and J.R. Moon, Journal of Microscopy, vol. 96, part 3, December 1972, pp. 381 - 384
[Sources: PNG; British collector known to the editor; plus those sources already mentioned in the text]
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A map of China reproduced with permission from Map of China by Tourizm Maps © 2006
An artificial bubble due to the language barrier and the management of tourist guides surrounds foreign tourists during their visit to China. So the brief impressions formed by the editor during a visit in June 2007 have to be treated with care. Where possible these impressions have been confirmed with information from other sources.
This is a vast and fascinating country whose population of 1.3 billion constitutes about a fifth of the total world population. The majority of the population still live in the countryside but this is changing rapidly with the breakneck growth of China's economy over the last twenty years. The visit was geographically widespread, including Beijing, Guilin, Chongqin, Wuhan, Nanjing and Shanghai, but it was mainly based in urban areas.
The most striking impression was the concern of all the Chinese met about the authenticity of the fifty and the hundred yuan banknotes. All larger shops checked these notes with a counting/authentication machine. Market and street peddlers were very reluctant to take notes of this value, usually requesting smaller denomination notes. The editor has not experienced this level of concern about the validity of a currency before. Even allowing for the fact that in Chinese terms these are quite high value notes this widespread concern must point to a very serious loss of confidence with the currency system.
In February 2007 the "China Daily" quoted Ma Jing, president of the Guangzhoa Branch of the People's Bank of China, as saying, "more than 540 million yuan [69.23 million USA dollars] worth of counterfeit currency was seized across the country last year, up 20 percent from the year previous." Police in Guangdong seized more than eighty percent, 450 million yuan, of this total. Guangdong is the large province containing cities such as Shanghai, Guangzhou [previously known in the west as Canton] and Shenzhen. It surrounds the former colonies of Hong Kong and Macau. The article does not make clear whether these are the number counterfeit notes seized in police operations or are the total number of counterfeit notes found including those identified in circulation by financial institutions.
The highest denomination circulation Chinese coin is the one-yuan. This is made from nickel-plated steel. Its nominal weight is 6.05g and its nominal diameter is 25mm. The editor weighed five coins of different year dates and found they had a range of 5.96g to 6.15g. The diameters of these same five coins ranged from 24.99mm to 25.02mm with no more than 0.01mm difference within the same coin.
The editor did not receive many circulation coins during his visit. Those he received were mainly one-yuan coins and these appeared to be genuine. They had all been recently produced, the oldest coin being dated 2001. These coin were not struck with significant depth. This shallow striking and edge lettering that is difficult to read with the unaided eye mean that these coins are probably relatively easy to successfully counterfeit.
In an article in the Shezhen Daily in 2003 a "pay-as-you-enter" minibus owner complained that twenty in every one thousand one-yuan coins was counterfeit. This is about two percent. The editor did not sense the same public unease in handing coins as in handling banknotes. This may be due to the much lower value of the coins.
An article in the "China Daily" in July 2007 gave significantly more information about the business of counterfeiting Chinese one-yuan coins. The author had interviewed two employees of a counterfeit coin "retailer". They were responsible for selling the counterfeits to small retail shops and snack bars for about thirty-five fen [10 fen=1 jiao; 10 jiao=1 yuan]. They claimed that "retailers" advertise with wall posters and on the Internet.The article describes how the "retailer" bought the counterfeits from a "wholesaler", Shun Ge, who was considered a major operator. Shun had relocated from Guangzhou, Guangdong province because of police activity. He was now located in Wuhan, the capital of Hubei Province; this lies to the north west of Guangdong Province. Shun told the paper that he bought the counterfeits from manufacturers in central Hunan Province and sold to cities in Guangdong and Hunan provinces. It was claimed most "wholesaler" purchase from Hunan Province.
Shun claims that he only bought counterfeits "from the best manufacturers", and that "Most coin identification machines cannot detect them from genuine ones." Presumably this means the counterfeits are made from the same type of nickel-plated steel as the genuine coins.
The Ministry of Public Security has listed eight cities as major targets in a police crackdown. These include Guangzhou and Wuhan. Several counterfeit factories in Hunan were raided. In one factory eight tonnes of counterfeits were seized, that is over one million fake coins.
[Sources: China Daily, February 2007 and July 2007; Shezhen Daily, December 2003; editor]
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COUNTERFEITING SNIPPETS FROM AROUND THE WORLD
In the report on Sasanian counterfeits in the last newsletter the editor overlooked an IAPN Antiforgery Committee's 2002 report. This was published in the November 2002 edition of the Counterfeit Coin Bulletin. They describe a number of Khusru II (Year 36, A.D. 590-628) dinars that first appeared on the market in 1992. They were described as: "..caused consternation as they appeared too good to be true, looked modern and generally unlike any other Sasanian gold coins, not least in fabric."
The IBSCC was asked to give an opinion on the coins. "The Antiforgery Committee's general feelings was they were probably false." Metal analysis indicated significant differences from Khusru II gold but similarity to contemporary Byzantine coins. The Committee acknowledged that there was a body of opinion that disagreed with them but considered it was time they reported.
[Source: Counterfeit Coin Bulletin November 2002 - Vol.III, No. 2]
Sasanian coin enthusiast will probably know that the British Museum is undertaking the "Sasanian coin project". This project is due to be completed in 2008 and plans the publication of a three-volume catalogue of Sasanian coins in the National Museum of Iran and the British Museum. "Each coin will be illustrated and described in the catalogue and the information will also go on-line."
Head of Turkish Archaeologists says many fakes on display in museums
Emine Aynur, president of the Turkish Association of Archaeology and Archaeologists, is quoted by Today's Zaman as saying that many items exhibited at museums and sold at auction were reproductions. Aynur claimed that in regions such as Antalya and Antakya, workshops existed to mass-produce fake items. She said that items were often accepted by museums without detailed examination due to a lack of qualified staff. Only museums in Istanbul and Ankara had any coin experts. Aynur added: “There are only a few coin experts in Turkey. So, there are many fake coins."
[Source: Today's Zaman, 19 February 2007]
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Appeal for assistance with book on Anglo-Saxon replicas and counterfeits
Tony Abramson, author of "Sceattas: An Illustrated Guide", is planning a companion volume that will include as much detail on replicas and counterfeits as possible. He states that, "I have been very concerned at the number of Ashmore replicas and chemically-etched Museum Reproduction Ltd replicas appearing, mainly on eBay but also on websites...and being sold as genuine." He would be interested in hearing from anybody who has relevant material, images or information. He can be contacted via the editor or by emailing: email@example.com.
April 2007, Greek police arrested the owner of a jewellery store and her supplier for the possession of illegally acquired antique coins and hundreds of counterfeit ancient coins.
Bulgarian author, Ilya Prokov, has posted a short illustrated article on the Forum Ancient Coins website showing artefacts left by modern engraving machines on counterfeits.
Why did a rare Greek coin did not sell in a London auction? Was it because its authenticity was questioned on a website?
On his excellent site on Irish coins John Stafford-Langan gives some details of some fake 1941 Irish farthings. He says these are the first struck fakes of the Irish modern series found.
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The euro counterfeit coins withdrawn from circulation in 2006
The number of euro counterfeit coins found in 2006 increased yet again. The total annual increase between 2005-2006 being sixty-three percent compared with thirty-five percent between 2004-2005. It is too early to be sure of a trend but the suspicion is that the rate of increase is itself increasing. It is now obvious that the counterfeiters' main target is the 2-euro coin. Counterfeit 2-euro coins constituted over 86 percent of the counterfeits found. Unfortunately the number of illegal mints being found appears to be reducing with just one Italian illegal mint raided in 2006.
The corresponding total number of counterfeit euro coins withdrawn in Germany was:
2003/16,500; 2004/51,000; 2005/46,300; 2006/76,866.
In March 2007 "The Resident" reported that Spanish police had broken up a large network of fraudsters on the Costa del Sol. The fifty Romanians and five Spaniards were involved in numerous activities including counterfeiting two-euro coins. A 2.5 tonne hydraulic press was seized.
New estimate of counterfeit circulating UK one-pound coins released
The Royal Mint released the results of a survey of counterfeit one-pound coins in circulation in 2006 to a Welsh regional ITV programme in June 2007. They found seventeen counterfeits per thousand coins, which is 1.7 percent. This is an almost doubling of the results in previous surveys. It is strange that this result was not released in the form of an answer to a Parliamentary question, which has been the previous practice.
Reports were seen concerning counterfeit Pakistani Rs 5 coins; fake Israeli 5 shekel coins circulating in the occupied Palestinian territories; yet more counterfeit Philippines 10 peso coins; counterfeit Canadian 2 dollar coins; and counterfeit USA quarter dollars used for Laundromats in Texas.
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Nineteenth century books and journals on-line
More and more out of copyright, numismatic books and journals are becoming available on-line. To those numismatists without very deep pockets these were previously only available in libraries. Ed Snible has produced a comprehensive guide to the issues of the Royal Numismatic Society, Numismatic Chronicle, available on-line. He list issues available either on the Internet Archive or Google Books. There are pro's and con's for each system in terms of ease of use, time taken to download etc. The reader needs to find which system suits them best. The main drawback currently is that the inability to search the whole series together and then just examine one individual article. Ed includes advice on using the ANS Library site to search for relevant information in the series and how to overcome copyright restrictions for some non-USA residents.
The Rev. Roger Ruding's "Annals of the Coinage of Great Britain and its Dependencies" is one of the landmark publications on British coins. The third edition of volume 2 published in 1840 can be found on Google Books at this link. This covers milled coinage from Charles II to the early part of Victoria's reign.
Sources from the nineteenth century have to be treated with some caution as modern scholarship has often changed previous conclusions. However they are a valuable resource and it is fascinating to follow the gradual accumulation of numismatic knowledge over the century.[Sources: http://www.snible.org/coins/ and Google Books]
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"Appendix 2: Examination of two counterfeit
coins from hoard 1" K. Eremin and J. Tate, pp 21-25
[Appendix to "Two denarius hoards from Birnie, Moray" N. M. McQ. Holmes, British Numismatic Journal 2006, vol. 76, pp 1-44]
Two hoards of Roman denarii were found at Birnie near Elgin, Moray, Scotland. The main paper is concerned with describing and documenting both hoards. The first hoard was found between 1996 and 2000. Appendix 2 describes the examination of the two counterfeit coins found in this first hoard.
The first counterfeit was "extremely deteriorated and fragmentary". It was believed to be a copy of a Flavian denarius. A genuine coin would date from 69-96 A.D. The condition of the counterfeit made it difficult for the authors to be definitive but they believed it was "a cliché-type forgery". This type of counterfeit is defined in the paper as "a thin foil of silver or copper alloy over a lead-tin core".
The second counterfeit was in "good condition" and identified as a counterfeit of a Domitian denarius. A genuine coin would date from 95-96 A.D. This counterfeit was considered to be cast and the composition suggests it may have been made from scrap derived from genuine Domitian denarii.
This paper contains xrfs analysis results, a discussion of comparative results from the literature, scanning electron microscope photographs  and an elemental profile of the cliché counterfeit. This is only a short appendix but appears to be an exemplary piece of work.
"Counterfeit coin of the realm - Review and case study analysis", Gagg, C.R. and Lewis, P.R., Engineering Failure Analysis, 2007, vol.14, pp1144-1152.
[The printed paper is due to be issued in September 2007 but it has been available online since January 2007]
The authors of this paper are from Britain's Open University. The paper reviews the counterfeiting of the British one-pound coin since its introduction in 1983. The main section of the paper consists of a detailed scientific examination of a single representative from each of the two main classes of these counterfeits. They examined a cast lead/tin counterfeit and a struck nickel brass counterfeit. This included measuring physical parameters, such as weight, diameter and hardness, energy dispersive x-ray spectroscopic analysis and metallography examination of cross sections of the counterfeits.
Dr. Gagg's main academic interest is in the forensic metallurgical analysis of failed metal components. So it is perhaps not surprising that the most interesting aspect of this paper is the metallography. The finding that the nickel brass counterfeit although a wrought product had a significant number of voids and contamination was new to the editor. The authors concluded this was due to the alloy having been produced by the counterfeiter rather than by a commercial producer. This may be pushing the evidence too far.
The editor must declare an interest; the paper as a reference for those seeking information on counterfeit coin, cites the Counterfeit Coin Newsletter. This does not prevent the conclusion that this paper is a very welcome addition to the rather small field of scientific literature on modern counterfeit circulation coins.
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The Infamous Ashmore Coins: Anglo-Saxon Pennies: Volume I
This is an ebook contained on a compact disc. It is produced by Alex Trussell of "blackmuuma" [an unfortunate choice of name] eBay Shop, price £5.99.
Sleeve of the compact disc containing the ebook.
This is the first disc of a three disc series planned by Alex Trussell. It contains images of 44 Ashmore replica pieces in a FlipAlbum 6.0 format. It is suitable for running on a PC with Windows 98/2000/ME/XP. Each "page" contains an image showing both sides of one replica plus the details of the supposed king/issuer and moneyer. The FlipAlbum contains two contents pages with each piece listed with a thumbnail image and an index. The rulers covered range from Aethelbehot to Edward the Confessor and an unnamed Viking ruler. It contains no introduction or explanatory text and no details such a piece weight or die axis. This also means that there is no explanation as to the sources of the images. Mr. Trussell does sell a number of Anglo-Saxon pieces labelled as Ashmore replicas on his eBay site.
The editor had had no experience with the FlipAlbum format but found it easy to use. It allowed a full screen display of the two sides of a piece. The format does not allow one to enlarge a specific feature beyond this size. The images were reasonable sharp and adequate for the enlargement allowed. The lack of an explanatory text and piece details does limit the interest and usefulness of the disc. However for those intending to purchase Anglo-Saxon coins on the web it could be a useful reference of pieces to avoid.
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Contemporary counterfeits of ancient coins usually consist of a lower value metal core with a coating of precious metal. Over the last thirty-five years a number of centres have applied advanced scientific procedures to investigate how these counterfeits were produced. One of the most prominent centres in this research has been the British Museum. References to some of the papers from the British Museum can be found at Science and coins on this site. Previous editions of this Newsletter have covered more recent papers published by other institutions.
A contemporary copy of a Roman Republic Furius Brocchus denarius. A genuine coin would date from about 63 B.C. The damage part at the bottom of the coin clearly shows a silver coated outer section with a corroded copper metal inner section. Dr. Kraft has estimated the silver foil thickness at 80 microns. The image is reproduced by kind permission of Dr. Kraft. Left click on the coin to access a larger image.
Dr. Gunter Kraft of the Technical University of Darmstadt, Germany, contacted the editor with some links to his institutions recent work on this subject. The first link was to a series of PFD files that contain a copy of Dr. Kraft's PhD thesis on the scientific examination of 35 contemporary counterfeits of Roman silver coins. The thesis is in German with an English language abstract. The thesis is worth examining for the quality of the illustrations even if the browser does not understand German. The second link was to a paper published last year in Archaeometry on ancient serrated denars. The paper is one of those discussed below.
A number of authors from the Technical University of Darmstadt have published five original papers on this subject over the last ten years. The team members changed with time but included, current department head Professor Dr. Hugo Ortner and experienced German numismatist, Dr. Fritz Reiff. A paper summarising their work over this period can be found at this link. This is a PDF file and is in German but is only three pages long and translation sites such as AltaVista's Babel Fish or Google's translation tool do make a rough but understandable English translation of the paper.
The editor has read the last four of these papers and has attempted to discuss some of the main points below. The authors used non-destructive techniques such as X-ray Fluorescence Spectrometry (XRF), Scanning Electron Microscopy (SEM), and Electron Probe Micro Analysis (EPMA). They also used a destructive technique known as Secondary Ion Mass Spectrometry (SIMS). The damage produced by SIMS is a crater of about 100 microns diameter or smaller. This is only just visible to the unaided human eye. SIMS produces data on elemental depth profiles and the authors claim this is the first time it has been used on ancient plated counterfeits.
The first two papers investigated gilded ancient counterfeits. The second paper of these papers is:
"Investigation of contemporary gilded forgeries of ancient coins" by F.Reiff, M.Bartels, M.Gastel and H.M.Ortner
Fresenius J. Anal. Chem. (2001), 371, pp1146-1153[in English], abstract at SpringerLink.
The authors state in the paper, "..contemporary forgeries of ancient gold coins are very rare compared with those of silver coins." Dr. Reiff purchased four examples of gilded ancient counterfeits through the coin trade. These were a Persian Empire Daric, a Greek Alexander gold stater and two solidi of the late Roman Empire. These counterfeits were found to have been produced by three of the many different techniques that had been described by Oddy and Cowell in their 1993 review [note 1].
The Persian Empire daric was found to consist of a 5-10 micron coating of a 94% gold alloy on what was considered to be a genuine silver Siglos coin. The authors believed that this was the first description of such a counterfeit. The coating was considered to have been built up by applying layers of gold leaf on top of each other. The individual layers of gold leaf were found to be each approximately one micron thick. The authors did not reach a conclusion as to how the films adhered to the underlying silver. However they did note Oddy and Cowell's description of forming a bond either by heating the coin to form an intermediate gold/silver binding layer or the use of an adhesive such as gum arabic.
The authors concluded that the counterfeit stater consisted of a silver core covered by an 89% gold alloy foil. Oddy and Cowell defined a foil as a sheet of metal of a thickness able to self-support the weight of the metal core it contained. The authors estimated the thickness of the gold alloy coating to be about 25-30 microns. Foil coating is usually carried out on the coin blank before striking between dies.
The solidi were concluded to have been fire gilded, in the one case onto a silver core and in the other onto a copper core. Fire gilding consists of coating the core with a liquid gold/mercury amalgam and then heating the piece to drive off the majority of the mercury. The detection of mercury in the coatings is usually taken to indicate fire gilding.
Note 1, Oddy, W. K. and Cowell, M., "The Technology of Gilded Coin Forgeries", Metallurgy in Numismatics, volume 3, 1993, pp 199-220 + plates.
"Investigation of contemporary forgeries of ancient silver coins" by Gunter Kraft, Stefan Flege, Fritz Reiff, and Hugo M. Ortner
Microchimica Acta (2004), 145, pp 87-90[in English], abstract at SpringerLink.
The authors examined three Roman counterfeit coins owned by a private collector:
1. C. Mamilius Limetanus denarius serratus; a genuine coin dates from about 82 B.C.
2. C. Sulpicius Galba denarius serratus; a genuine coin dates from about 106 B.C.
3. Septimius Severus denarius; a genuine coin dates from between 193-211 A.D.
The first counterfeit was examined alongside a genuine example. This first counterfeit had serrated edges, that is, irregularly spaced notches around the edge. It was fragmented allowing the authors to saw across the piece, polish it and scan across this cross section. They found a silver/copper alloy coating surrounding a copper core. The coating varied between 70 to 150 micron on the faces and between 250 to 300 micron on the outer edges. Only a low level of mercury was found in the silver layer. This and the thickness of the silver layer led the authors to consider the most likely production technique was foil coating. The authors considered that the extra thickness at the edges could have been due to silver being squeezed to the edge during striking. However they found evidence of a triple over lapping of the coating at one point on the edge and this may be a more likely explanation. No conclusions were made about the method of attaching the foil coating to the copper core.
The second counterfeit also had serrated edges. It had a missing fragment revealing a copper core with a silver/copper alloy coating of about 75 to 80 micron thickness. Again the silver coating had a low level of mercury present and it was concluded that this was a foil coated counterfeit.
This photograph shows a genuine Septimus Severus Legionary denarius described in detail at this link. The image is reproduce with the kind permission of James Grout.
The dark surface of the third counterfeit consisted mainly of tin, lead and copper. It was concluded that this counterfeit consisted of a copper core coated with a lead/tin alloy to originally give the appearance of a white silver coin.
"EPMA Investigation of Roman Coin Silvering Techniques" by Gunter Kraft, Stefan Flege, Fritz Reiff, Hugo M. Ortner and Wolfgang Ensinger
Microchimica Acta (2006), 155, pp 179-182[in English], abstract at SpringerLink.
This paper is an examination of the use of electron probe micro-analysis (EPMA) for the investigation of Roman coin silvering. Two of the coins investigated were similar, if not the same, as those in the previous 2004 paper. This paper will not be of great interest to those who are mainly concerned with counterfeit coins and their production techniques rather than the scientific techniques used.
"Analysis of the Notches of Ancient Serrated Denars" by G. Kraft, S. Flege, F. Reiff, H. M. Ortner and W. Ensinger
Archaeometry (2006), 48, 4, pp 605-612[in English], the full paper can be viewed at http://www.tu-darmstadt.de/fb/ms/fg/ca/arch_275.pdf.
This paper is a continuation of one aspect of the work reported by Kraft et al in their 2004 paper. Six serrated Roman coins were examined including three described in the 2004 paper. The three addition coins examined included a counterfeit C.Problicius denarius serratus. A genuine coin of this type would date from 80 B.C. Roman serrated denarii were produced between about 211 B.C. to about 78 B.C. There has been no agreement as to whether contemporary counterfeits of these coins were silver coated within the notches and the process used to make them.
The authors found that at the bottom of the irregularly spaced notches of these coins was a silver coating. This was of about 5 to 10 micron thickness. They concluded that the notches had been formed by initial foil coating a coinage blank and then by a number of individual forging operations on the edge prior to the striking of the design onto the faces of the coins. They believed that the forging operation produced a thin foil coating in the notches. They found no evidence to indicate that the silvering of the notches was produced by a different technique to the main surfaces of the coin.
Some general comments
This series of papers is welcome in extending our knowledge of the contemporary counterfeiting of ancient coins. The pieces examined originated in the coin trade so perhaps some of the results do need confirmation by counterfeits from other sources.
The use of SIMS offers a technique that although destructive makes significantly less damage than one of the alternatives, which is taking a cross section of a coin. Unfortunately SIMS does require a very sophisticated and expensive instrument and this will probably not allow its wide spread use on counterfeits.
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