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No. 13 January 2010
COUNTERFEITING SNIPPETS FROM AROUND THE WORLD
"Newton and the Counterfeiter" by Thomas Levinson
"Using the optical mouse sensor as a two-euro counterfeit coin detector"
"Laser and electron beams physical analysis applied to the comparison between two silver tetradrachm Greek coins"
Once again the Counterfeit Coin Newsletter, CCN, has attempted to bring together a cross-section of counterfeiting news from across the numismatic world.
Misinformation on the internet
The danger associated with the rapid reproduction of out of context information across the internet was illustrated in November 2009. An article appeared in "Science Daily" describing a Spanish research paper that had appeared in the scientific journal, "Sensors" [see IN PRINT below]. This article stated that, "..some optical mice can be used to easily and cheaply detect counterfeit euros". The information in this "Science Daily" article was then reproduced in general and coin magazines and forums across the web e.g. Numismaster.
The problem with this is nobody appeared to go back to the original scientific article. This clearly states that the method was able to identify the vast majority of local class (usually cast) euro counterfeit coins but only 24 percent common class (struck) euro counterfeit coin. Regular readers will be aware the vast majority of euro counterfeit coins are the struck, common class types. So despite the fuss on some of these sites, this technique, as reported, is of limited use in identifying counterfeit euro coins. It is to be hoped that this type of reporting will not undermine the investigation of automatic, visual techniques for identifying counterfeit coins. CCN certainly hopes that this may be the way forward in automatically identifying the many counterfeit one-pound coins that currently cannot be identified by electronic sensor methods.
Photograph of a Serbian "Hoard" fake Constantius II with gateway reverse, reproduced with the kind permission of Wildwind website from http://www.wildwinds.com/coins/ric/fakes2009.htm
In the summer of 2009 a supposed "hoard" of late Roman copper coins was sold from a German source. This "hoard" was supposedly found in Serbia and was described as, "found a few kilometres to the south of town in a depth of three metres. Since thereís no oxygen in this depth, no harmful corrosion could occur. Thatís the reason why all coins - as usual for hoard coins - have an extremely fine, perfect condition." Warnings about this "hoard" were soon being posted on both the Ancients.info and Forum Ancient Coins forums.
V Coins dealer, explained on Ancient.com,
"Getting to the point and trying to explain why I feel every piece is fake even though I'm only looking at a photo:
These conclusions based on photographs now appear to have been confirmed by examination in-hand, resulting in some of the "hoard" being sold as modern copies. For those interested in seeing more examples of these counterfeits Matter Richter has posted a gallery of examples from this "hoard".
The emergence of this "hoard" illustrates the need for dealers and collectors to only purchase material that is well provenanced and has appropriate export licences. Without these records such coins are likely to have been smuggled or counterfeited. It continues to amaze CCN that people who would not contemplate breaking the domestic laws of their country are happy to buy and sell such material from a probable illegal origin.
[Sources: http://www.wildwinds.com/coins/ric/i.html, Ancients.info, Forum Ancient Coins, CFDL.]
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PCGS coin grading and authentication services have posted an article about their guarantee and changes in the way it deals with World coins and copper coins. PCGS now limits the guarantee on non-U.S. coins to $10,000 per coin, with a limit of $1,000 per coin for Chinese coins.They state that, "In the past 24 years, PCGS has paid out $7,320,437 under the terms of the PCGS Grading Guarantee". This amount is so large because, "if we make a mistake...[we compensate] with an actual cash guarantee for the market value of the coins we grade and authenticate." The press release then describes the twelve most expensive mistakes they have made. These include authenticating five coins that subsequently were identified as counterfeit. PCGS described these counterfeits as:
"1849 Mass & Cal $5 AU55 $150,000, June, 2006. This is a very rare territorial gold coin that turned out to be counterfeit."
"1861/57-S Clark Gruber $20 MS63 $75,000, November, 2007. This coin had been known to the coin community for decades. In fact David Hall had it at coin shows for sale in the mid-1970s. But research eventually showed that this coin, and several other Clark Gruber rarities, were actually counterfeits that were probably made in the 1950s or 1960s."
"1861 Clark Gruber $20 (three) MS62s $55,000 each, January, 2008. Same type of circa 1950s counterfeits as coin above."
PCGS have not been prepared to tell the CCN details of the research evidence against these items. Presumably it is part of the belated attempts by the USA's coin community to deal with the legacy from the "Franklin Hoard" and other spurious early western coins. The "Franklin Hoard" originated with Paul G. Franklin and was marketed by John J. Ford. Some of the research on these items was commendably documented in the E-Sylum in 2008, volumes 31 to 34. The main forum for considering some of these early western pieces has been the Pioneer Gold Forum. This group of experts was brought together by Don Kagin under the auspices of the "Society of Private and Pioneer Numismatists", SPPN. Kagin told the ESylum that, "the $20 1861 Clark Gruber & Co. Proof-like ... issues...were discovered in the late 1950s but the origins seem to have been Jack Klauson from an old guy in Denver, or so he told me...A unanimous determination was made that the coins in question were 20th century Fantasies made for collectors." This decision was made in the early part of 2008. PCGS are now labelling these proof-like 1861 Clark Gruber $20 coins as fantasy pieces in their registry.
Over the years this issue has become interwoven with personality clashes etc so it is important to name those making these decisions. Kagin reported that the members of the Forum were:
* Andy Lustig
Members not attending the Forum (but participating in viewing and chatting):
* David Camire
Non-members invited to attend who participate by either examining the coins and material or commenting at the meeting:
* George Fuld
Counterfeit Coin Newsletter No.11 reported,
"In August 2008 a
press release from Kagin's announced that
the SPPN had determined that the so-called United States Assay Office proof gold $20 were "Transfer Die Forgeries"."
The E-Sylum reproduced a discussion "in the Colonial Newsletter Foundation Google groups,
where George Fuld revealed:
"I started this coin study of the so-called proofs in early 1964 with a group Made up of Dr. James O. Sloss,
Abe Kosoff, Eric Newman and myself. As a public service, the Metallurgy Research Laboratory of the Goodyear Tire and Rubber Co.
did x-ray studies and photomicrographs and back scatter x-rays. All data was transmitted to Eric about six months
later and he carried the ball up to the 1967-8 PNG hearing. One proof was sent to the Secret Service--but they declined
to study it as they claimed that the USAO was not a government Mint until 1854 although the USAO
was a US government agency."
"I started this coin study of the so-called proofs in early 1964 with a group Made up of Dr. James O. Sloss, Abe Kosoff, Eric Newman and myself. As a public service, the Metallurgy Research Laboratory of the Goodyear Tire and Rubber Co. did x-ray studies and photomicrographs and back scatter x-rays. All data was transmitted to Eric about six months later and he carried the ball up to the 1967-8 PNG hearing. One proof was sent to the Secret Service--but they declined to study it as they claimed that the USAO was not a government Mint until 1854 although the USAO was a US government agency."
1. "Paul Garland of Tennessee as a claimant asserted that a "proof" 1853 $20 USAOG coin sold to him in 1965 for $3,000 by Tom Ryan of Illinois was a fake and an arbitration was arranged by PNG in 1966... When Paul Franklin was a witness he was asked the details of the source of the "Franklin Hoard" $20 USAOG pieces including the coin under review. Franklin refused to answer and his representatives asserted that no dealer should be required to disclose his business sources."
2. "During the arbitration proceedings it was pointed out that the coin under review and all other known pieces from the "Franklin Hoard" $20 USAOG pieces had 170 reeds on the edge rather than 164 reeds on previously known 1853 $20 USAOG pieces: and also that on at least one of the "Franklin Hoard" pieces there appeared on the face a thin weak incused compact helical or spiral line which seemed to be on the planchet prior to striking. The helical line was asserted to be have been applied by an automatic crosscut lathe."
3. "Two of the arbitrators informally agreed that the piece under review was a forgery but the third would not agree. All three arbitrators finally agreed in 1967 that the coin was not a "proof" as stated on the invoice".
4. "Many years passed before the forgery issue arose again. Some of those asserting forgery included Fuld, Bressett, J. P. Martin, Buttrey, Kleeberg, and Dannreuther. Others continued to urge genuineness. There were several vigorous debates and extensive publications. When the identical dents were noticed about 1994 on all known "Franklin Hoard" $20 USAOG pieces the diagnosis of forgery seemed reconfirmed. Then at the 2008 Baltimore session the prototype piece for the forgeries (containing the same dents and with 164 reeds on the edge) was presented, having been located by a member of Don Kagin's firm. A span of over 40 years was needed to produce general acceptance of forgery of "Franklin Hoard" $20 USAOG pieces."
Don Kagin said that, "Our next project will probably be another subset of .Ford discovered. issues ... USAOG coinage and ingots. As you know Ford, who was one of my advisors for my Pioneer book, could be very persuasive and most of us including Harvey Stack, Dave Bowers, my father and I believed most of what he said. Others, like Walter Breen, I now conclude, while having issues with John, feared him."Note 1: see the paper Western Precious Metal Ingots: the Good, the Bad & the Ugly Aug. 2003, by Fred Holabird, Bob Evans & Dave Fitch.
Note 2: Kleeberg and Buttrey's site on the "False Western Bars" etc. does not appear to be currently accessable but Kleeburg has a pdf document covering similar ground. For those still wishing to consult Kleeberg and Buttrey's "How the West was Faked" Google this title and click on the Google cache rather than the website.
[Sources: PCGS, Kagins Inc., E-Sylum]
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The above photographs show a 2007 dated counterfeit one-pound coin found in Shepherd's Bush Market, London, in August 2009. The coin had the correct alignment and weighed 9.295g.
This video, showing Professor Colin Gagg of Britain's Open University talking about counterfeit one-pound coins, was posted on YouTube in 2009.
The British Treasury posted a number of documents onto their website in January 2010 in response to a "Freedom of Information" request by an unknown party. The documents consist of a thirty-page narrative group of minutes and memos from November 2008 to May 2009. Also posted were the last three of the Royal Mint's reports of their six-monthly surveys on the number of counterfeit one-pound coins found in circulation. Individual names and the names of propriety instruments and equipment have been hidden in the documents. However apart from this, they presumably present all the documented information concerning the counterfeit one-pound coin problem involving HM Treasury over this period. It is usual to exempt advice to ministers in such cases.
The first narrative group document is the minutes of a meeting between HM Treasury and the Royal Mint, APAC (the group representing banks, cash centres etc.) and SOCA (the Serious Crime Agency) on the sixth November 2008. The meeting chairperson opened the meeting by stating that it was, "the first opportunity that all parties had met to discuss the issue". The meeting chairperson also advised that, "the issue of counterfeits had achieved" (a) "level of political significance and the Treasury Minister had been briefed accordingly." For those wondering what had caused this "level of political significance" they should remember that on 22nd September 2008 Ben Ando's BBC News report was broadcast and subsequently picked-up by most of the British media. So although the problem of one-pound coin counterfeiting had been becoming more and more serious since 2002 it was only after it became a major news story that HM Treasury felt the need to rouse itself.
For the record these documents tabulate all the results of the Royal Mint's surveys of the number of counterfeit one-pound coins in circulation.
These documents also record the annual number of counterfeit one-pound coins withdrawn and sent to the Royal Mint for destruction. It is obvious that in 2008-2009 the banks and cash handlers suddenly awoke to the need to start removing more of the counterfeit coins from circulation. The documents appear to imply that this increase came with a problem of increasing numbers of genuine coins being wrongly identified as counterfeit.
The documents show that only about ten percent of the one-pound coins passing through the cash centres were authenticated in automatic machines. These machines were only identifying about thirty percent of the counterfeit coins they examine. There did not appear to be much confidence that this figure could be increased with the current technology. APACS which has now renamed itself the Payments Council said in a letter they sent to HM Treasury on the 27th November 2008 that, "..the unpalable fact is that good quality counterfeits cannot be identified by machine". The Royal Mint in a briefing paper to HM Treasury admitted that full authentication by the current machines would, "..reduce the counterfeit level to around two percent." This estimate seems to ignore the future input of further "good quality counterfeits" into the system.
Other points from the documents include:
Another six months news on one-pound counterfeiting
August 2009 to January 2010 provided news of many developments in the UK's counterfeit one-pound problem. This news seemed to vary from the serious through the frivolous to the farcical.
In September 2009 the operator of the Mersey Tunnels, Merseytravel, announced that £86,000 of counterfeit one-pound coins had been passed in their tollbooths in the previous six-months. A spokesman said that the counterfeits, "were detected by sophisticated electronic equipment in the cash collection system." It is believed this equipment was used after the counterfeit coins had been accepted by the operator.
Police forces in a number of areas of the UK issued warnings about high levels of counterfeit one-pound coins circulating. These areas included Lancashire, the Isle of Man and Ulster. An initial police warning in Ulster caused chaos when the counterfeits were identified as being bright and shiny and with no beads around the rim. This resulted in many shops and customers refusing to accept the genuine 2008/9 Matthew Dent designed one-pound coins. These, of course, are bright and shiny and have no beads around the the rim. It required the Royal Mint to issued a clarifying statement to prevent this farce deteriorating further. A BBC Northern Ireland news story and video covers this very well.
In December 2009 two cases involving the manufacture of counterfeit one-pound coin came to court. The first case at Maidstone involved an illegal mint found in Kent. A 49-year old man pleaded guilty to two charges of making counterfeit £1 coins, and having counterfeiting materials. His uncle was found not guilty and the jury could not reach a verdict on his father. There is likely to be a retrial of the 70-year-old father. £8,000 of struck counterfeit coins were found at this mint along with 14,000 coinage blanks.
In the second case, Yasin Patel, 45, of Blackburn, pleaded guilty at Sheffield Crown Court to three charges of conspiracy to supply counterfeit currency. The case involved both counterfeit banknotes and coins. Patel was accused of being part of the gang supplying the north-west of England with counterfeit bank notes obtained from London. He was also accused of manufacturing one and two-pound counterfeit coins. He supposedly melted metal on a stove and cast it into molds to produce the counterfeit coins. He then used electroplating equipment to coat the counterfeits. 6,000 counterfeit one-pound coins were seized. Mr. Patel's sentencing was deferred. He had previously been part of the so called "Heckmondwicke counterfeiting case" in 2000.
Coin handling equipment company, Willings Services Ltd, have posted on to the web a catalogue of the counterfeit one-pound coins they have identified.
"Brian" has started a FaceBook site calling for a boycott of one-pound coins because of the counterfeiting problem. He aims to get two million members for the group but at the time this newsletter was being published only 130 people had signed up for the group. CCN shares "Brian's" concerns but does not agree with his proposed solution.
Also see the November entry in the Diary section.
[Sources: HM Treasury, BBC News, Click Liverpool, Wirral News, Newry Democrat, Belfast Telegraph, Kent On-line, This is Kent, Blackburn Citizen, Willings, YouTube, Facebook]
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COUNTERFEITING SNIPPETS FROM AROUND THE WORLD
Countries that in recent times have needed to change their currency due to coin counterfeiting
In one of the briefing papers referred to in the report above on one-pound coin counterfeiting, the Royal Mint gave a brief summary of countries that had recently had to make changes in their currency because of coin counterfeiting. They said:
"There is no industry standard as to the number of counterfeits to warrant a recoinage. In 2002 both Jordan (1 dinar) and Hong Kong ($10) decided to issue banknotes when the counterfeit levels of the coins steadily increased towards five percent. South Africa decided to upgrade their 5 rand coin in 2004 at a lower level. Malaysia withdrew their one dollar coin in favour of a note in 2005. Whereas informal discussions with overseas Issuing Authorities indicate the maximum acceptable percentage is five percent, the countries listed earlier took action at a lower level."
Euro counterfeiting update
The number of counterfeit euro coins removed from circulation fell by 12 percent in 2009 compared with the previous year. This is the second consecutive annual decrease. Within the overall totals there were rises in the numbers of counterfeit 50 cent and 1-euro coins withdrawn but the drop in the number of 2-euro coins withdrawn was much larger.
The reasons for the reduction of counterfeits withdrawn from circulation are not readily apparent. No new illegal mints producing counterfeit euro coins were dismantled in 2009. Although there was some police success in disrupting distribution networks, it would appear most of the criminal groups responsible for counterfeit euro coins are still operating.
[Source: Europa press release Memo/10/2, 11 January 2010]
In New Delhi, India, a man was gaoled for three-years for selling equipment for making counterfeit 5 rupee coins.
There were further reports of seizures of counterfeit coins in China and Malaysia.
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An altered Canadian 1942 "filled die type error" 1 cent surfaces
Canadian collector, Peter Preston, sent details of an error coin he bought on eBay. The error was a supposedly 1942 coin having been produced with a 1912 date due to a manufacturing mishap. When Peter received the coin in-hand he posted images on to the discussion forum at http://www.canadiancoin.com/. The contributors soon expressed disquiet was about the coin. This caused Peter to get his local coin dealer to check it under a digital microscope. The opinion was that the coin had been altered from a standard 1942 one cent. Happily, Peter was able to return the coin and get a refund.
Peter also added that Canadian collectors still have problems with copy or counterfeit tokens especially Hudsons Bay Company tokens.
Counterfeits and altered coins encounted by the coin grading companies
Donn Pearlman has sent to CCN details from NGC and PCGS of counterfeit and altered USA coins they have recently identified.
Firstly from NGC are photographs of two counterfeits sold on-line
A photograph of the obverse side of a fake USA 1916-D dime.
A photograph of the reverse side of a fake USA 1916-D dime.
A photograph of the obverse side of a fake USA 1915-D gold Half Eagle.
A photograph of the reverse side of a fake USA 1915-D gold Half Eagle.
Secondly, Collectors Universe, Inc. and PCGS have release photographs of a tampered PCGS holder with a composite coin. They describe the items as, "These four photographs show a tampered PCGS encapsulation holder with a fraudulent insert. When the holder was cracked open it revealed that it housed the pictured coins, a genuine 1879 and a genuine Carson City Mint dollar that were split in two along the rim to create an "1879-CC." PCGS experts believe the diagnostic evidence indicates the 1879 Morgan dollar used in this case most likely was an 1879-S." PCGS would not say this but obviously this type of fraud is made much easier with a coin contained in a holder that does not allow the edge to be examined.
A photograph of the obverse side of the fake USA 1879-CC dollar.
A photograph of the reverse side of the fake USA 1879-CC dollar.
A photograph of the edge of the fake USA 1879-CC dollar.
A photograph of the fake USA 1879-CC dollar holder.
There have been further reports of Chinese counterfeit Spanish Mexico 8-reales coins.
A number of websites and forums have been awash with rumours about fake ingots and coins made from gold-plated tungsten. CCN has not found any verifiable facts to substantiate these rumours. However just for interest this is a link to a Chinese website that sells gold-plated tungsten items, http://www.tungsten-alloy.com/en/alloy11.htm.
Worrying query from a contributor to Forum Ancient Coins, "are the major auction houses really starting to slip and are letting more fakes through than usual?"
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A long annual holiday meant that coins and counterfeits were mainly swept off the agenda for the month. However my wife and I did spend two days of our holiday in the Bulgarian town of Nessebar [previously Messambria]. It is a strange mixture of a modern holiday resort with a large number of Unesco recognised ancient buildings. It contains a small but interesting Archaeological Museum housed in a modern  building. The museum had a number of cases of numismatic exhibits. For once I was able to buy at the museum a glossy booklet with illustrations of, "The Coins of Messambria". This made for a very worthwhile visit. A website on Nessebar can be found at http://www.ancient-nessebar.com/index.html
Most of this month was spent completing Newsletter 12. In between this I had to deal with a number of contacts with press and TV people seeking background information on one-pound counterfeiting. This website appears to have assigned to me the role of an unpaid research assistant to the British media. This I do not mind provided I can get the general public more aware of the problem of coin counterfeiting. What does irk me is the occasional timewaster.
12 October, I spent most of the day travelling to and from Staines, one of London's suburbs, to record a TV interview on counterfeit one-pound coins. The interview will be part of a short item in a series of programmes due to be broadcast on the BBC in the early part of 2010. I did some location filming for this programme earlier in the year and this added a number of interesting fake one-pound coins to my collection. One of these counterfeits came directly from a bag of coins issued by a well-known British bank.
I gave myself a small treat for Christmas by buying a cheap 1887 shilling to add to my small collection. I took a gamble and bought on eBay and it arrived just before the 25th December. It was as shown and described so no complaints, but in-hand it was obvious that it had been cleaned recently. I cannot understand this desire to have all silver coins bright white. The natural state that silver reverts to is a dark tone if not black. In my opinion some of the intermediate tones can be just as beautiful as a bright white colour. Of course there are some very ugly, blotchy toned coins but with time, further toning usually improves these.
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"Newton and the Counterfeiter" by Thomas Levinson
"Newton and the Counterfeiter"
by Thomas Levinson
Published by Houghton Miffin (USA) and Faber and Faber (UK) 2009; Hardback pp 318; UK recommended price £20
Issac Newton finished publishing his three volume masterpiece, "Philosophie naturalis principia mathematica" [usually known as "Principia"] in July 1687. At this time Newton was earning £100 per annum as the Lucian Professor of Mathematic at Cambridge University. With the help of his admirer, John Locke, he sort to improve his position and earnings by finding a suitable post in London. Finally in 1696 Newton was appointed as Warden of the Royal Mint with a annual income of £415. At this time the Royal Mint was governed by three officers, the Warden, the Controller, and the Master and Worker. The Warden was responsible for the Royal Mint's facilities and was it's official magistrate.
Newton held the position of Warden for four years before being appointed to the much more lucrative posion of Master and Worker. The Master at this time had an annual income of £500 plus a fee for every pound of metal coined at the Royal Mint. Thus Newton received £3,500 in his first year of the post and an average of £1,650 per annum until his death in 1729. These were large sums of money for this time and meant he became a very wealthy man. This book concentrates on Newton's four years as Warden. This period includes part of the 1690s, the author describes this decade as "the golden age of English counterfeiting". It tells of Newton's attempts to bring to justice William Chaloner, one of the most prominent of the counterfeiters.
Thomas Levenson is Professor of Science Writing at MITT. He has authored a number of books and science documentaries. He tells of these events in an accessible manner and draws an excellent picture of English society at this time. His descriptions of Newgate Prison and the informers and the justice system of the period are very well done. This book is recommended for anybody interested in coins, counterfeiting, history or just seeking an entertaining read.
"Using the optical mouse sensor as a two-euro counterfeit coin detector" by Marcel Tresanchez, Tomàs Pallejà, Mercè Teixidó and Jordi Palací, sensors, 2009, vol. 9, pp 7083-7096
Open access pdf paper at http://www.mdpi.com/1424-8220/9/9/7083/pdf.
This paper describes an attempt by Spanish researchers to use a pc optical mouse to authenticate 2-euro coins. Unfortunately, although able to identify "local class" [cast] counterfeit 2-euro coins, the procedure was only able to identify 24 percent of "common class" [struck] counterfeit 2-euro coins. The optical mouse contained a relatively low resolution CMOS camera viewing a 30 x 30 pixel infra-red illuminated image. This image only covered a small area of the coin so the coin was rotated under the optical mouse capturing more images and acquiring a much larger view of the coin. These images were then compared against templates of genuine 2-euro coins. Your editor is not qualified to comment on the mathematics of this comparison procedure.
"Laser and electron beams physical analysis applied to the comparison between two silver tetradrachm Greek coins" by L. Torrisi1, G. Mondio, A. M. Mezzasalma, D. Margarone, F. Caridi, T. Serafino and A. Torrisi, "The European Physical Journal D", 2009, vol. 54, pp 225-232
The main details in this paper appears to be the much the same as those published by four authors in the 35th EPS Conference on Plasma Phys. Hersonissos, 9 - 13 June 2008 ECA Vol.32D, P-4.170 (2008). A pdf copy of this shorter earlier paper is at http://epsppd.epfl.ch/Hersonissos/pdf/P4_170.pdf.
The two coins examined were a Messana [Messina] Anassila silver tetradrachma dated 470-466 B.C. and a counterfeit similar to this coin. The counterfeit was one of a "huge quantity of ancient counterfeit coins realised by a Sicilian forger.. They had been realized by strucking(?) or lost wax casting techniques..". Two techniques were used to non-destructively analyse the coins. Energy dispersive x-ray spectroscopy induced by an electron beam was used for a bulk analysis on the metal. The only surface preparation used was a gentle ultrasonic clean. The counterfeit was then sectioned and an estimate of the depth of its surface patina made. Laser ablation mass spectrometry (LAMQS) was used to evaluate the surface patina.
The authors concluded that the two coins showed "similar elemental composition". This is not unsurprising as an EDX analysis on an unprepared surface would at best only give an approximate analysis of the bulk coinage alloy. Your editor was also not convinced by the authors use of surface patina analysis to differentiate between the genuine and counterfeit coins. Unfortunately a genuine coin with an artificial patina is not unknown and perhaps one should remember the saga of the "Black Sea Hoard" before placing too much reliance on patina analysis.