Forgery Methods

Summary of discussion on CoinForgeryDiscussionList

From:  Alan VanArsdale (moderator)
Date:  Mon Feb 12, 2001 1:31pm
Subject: Filament Die Preparation

1. Obtain an authentic example of the series which it is desired to
copy with minimal die wear and minimal coin wear.

2. Mount the coin in the end of a short metal tube (tube of higher
melting point than bronze) at right angles to the walls of the tube.

3. Prepare a bundle of bronze filaments to fit in the tube, tightly,
but not so tightly as to not allow free movement.

4. Placing the filament bundle in the tube, tap the sides of the tube
repeatedly until the filaments settle onto the surface of the
coin. After this is done drive thin bronze wires into the filament
bundle until tight, the length of these wires about 90% that of the

5. Heat the entire apparatus but not too hot, to hold the filaments in

6. Remove the coin, and dust the coin end with a very finely ground
copper powder, stored after gringing in anaerobic conditions, while it
is still a bit to hot to touch.

7. Pour molten bronze on the other end of the bundle, the one without the 
coin image, repeat step 6 holding the image end up. 

8. Lightly polish the coin image end of the bundle removing loose
copper dust by dry air. The dust should permeate the interstitial
spaces between the bronze filaments.

9. Heat the assembly just to the melting point of copper keeping the
image end up the entire time.

10. Again polish the image bearing face of the die, removing excess

11. Placing a morphologically accurate mold of the coin on the image
end of the die, heat the entire apparatus to the point of plasticity
for the amalgum, image side down, for several hours.. Of course mold
is prepared by standard methods from non contracting materials of
higher melting point than bronze.

12.  Allow to cool over the correct period for maximum tensile strength.

13. Strike a number of coins with the die, and melt those coins (watch
your workers!!). This will cover signs of the process of manufacture
of the die on the finsihed product by natural die wear.

Advantages over poured dies (pouring liquid metal over a prepared coin cast)

1. Greater die strength and longevity, closer to authentic dies, if
done correctly.

2. Minimal contraction upon cooling of the metal, it is important not
to bring the fibers to liquid state in their cores. The pressure of
the compaction methods used will compensate some for any contraction.

This is a rough outline of the method, enough to rediscover the
process and make dangerous forgeries. Brought to you by forensic
science based upon examination of forgeries. If anyone wants to
discuss counter measures, other than by detecting that the coin is not
aged properly, post your observations or questions to this list and I
will try to answer them.

From: "Alan VanArsdale" Date: Tue Feb 13, 2001 8:52pm Subject: Method of gold coin Forgery This was provided to me by a person who wishes to not be identified. The applications go beyond what is apparent here, and I have heard rumors along these lines for several years. This is the most concise and, I think probably a very factual description, I have seen of the process. Probably many of you can imagine, in light of recent events, why this person wishes to remain nameless. Unedited transcript follows. << The modern forgers of gold coins have a new method of die production. You simply find a hoard of original high grade coins so that you get a good mix of dies. Than take the new plastic that dentists now use for fillings that had harden on exposure to particular types of light (any modern dentist should be able to provide the details). You impress a coin into the plastic and harden it with light and you have a die (it will take only a few seconds). Impress the other side the same way and in under a minute you have two dies. Do this with 100 different coins and in a couple of hours you have 100 sets of dies that can be mixed and matched so that your fakes are all different die pairs. What is really interesting is that each die is only good for 2 to 3 strikes before it breakes up, but as they can be replaced in seconds it does not matter, but the result is can they can strike three coins from the same set of dies and each strike will show a different die state. By mixing and matching 100 die sets, they can strike 300 coins without ever using the same die pair twice. If they then mix their 300 coins back into a hoard of 100 originals, they end up with 400 coins 1/4 of which are orignals, and the fakes all appear to share common dies with. >>
From: "Alan VanArsdale (moderator)" Date: 20001 Feb 14, 3:11pm Subject: Forgery Detection Metal Elasticity Probably most of you understand already it is possible to make dies which are for all practical purposes exact negatives of the coins they are copied from. This may inspire awe and fear in the numismatic community but things are not so bad as they may seem. There are aging processes in coins which can indicate authenticity or forgery/alteration, I will not touch upon that here. Such dies are perfect copies of coins, not the dies they were struck from. Struck coins are not perfect copies of the dies they were struck from. There is the obvious, mint luster, striations, flan cracks etc. But there is also metal elasticity, cold or hot metals have some elasticity (any which do not can not be struck into coins or they would shatter). When a coin is struck it returns to its original shape some (in the case of authentic coins a flat blank usually unless an overstrike). It also is bent and warped some depending on the force angle etc. of the die. The forger can cover this by double striking or other processes, but then the final strike will show less force than in an authentic coin. How to use this? Measure the elevation of the features a forgery is imitated from. In comparison the struck copy will have lower relief or elevation in those features. So rather than making lateral measurements, which will be about right, measure topographical distances. So the answer is a perfect copy of a coin in a die does not strike perfect copies of that coin. Measurements should me made in microns.
From: Dawson Lewis DawsonCoins@a... Date: 2001 Feb 16, 1:19am Subject: Re: [Moneta-L] How to make casts of coins? I have also made impressions of my coins using a material called "Scullpy". "Scullpy" is a "polymer clay" that stays soft until you bake it. Then it becomes ceramic hard. The key to making impressions was liberal doses of baby powder. After drenching the coin in baby powder I would blow out the clumps inside the letters. I made round "blanks" of clay. I found the thicker the clay the better. I would then firmly press the coin into the clay until it was sunk well beneath the top of the clay. The hard part was getting the coin out of the clay. What I recommend is taking a popsicle stick or tongue depressor and push down the clay around the edge of the coin. You end up with the coin surrounded by a larger ring. (Incidentally, this makes a nice area to hold plaster.) I found the best way to lift the coin was to lift a little bit at a time, working my way around the circumference of the coin. If you just lift from one side the opposite side digs into the clay. The better the coating of baby powder, the easier the coin came out. I did this with an ant. of Probus that was about 90% silvered. I did notice that maybe a few percent of the silver was lost. However, this might have happened when I rubbed the coin with a soft cloth to clean it. Once the "Scullpy" is baked, it is rock hard and makes good plaster of paris impressions. I have not seen any damage to the coins other than mentioned above. However, it might be even safer to use dental putty. This is the stuff my dentist used to make a mold of my tooth in order to prepare a crown. Because it is used in the mouth, you can be sure that it has few volatile chemicals that might trash your coins.
From: "David D." Date: 2001 Feb 24, 8:25am Subject: How hard to makes fakes, really... It has been suggested by knowledgeable people that the key difficulty in making a fake is the flan. Since you are evidently a chemist, I'll ask you and the list generically. I dont see why a metallurgist+chemist who also knows coins and perhaps has access to a machine shop could not do a very good job on fakes. At least well enough for 90% of us, which is completely sufficient for making lots of money. Crystallizing metal cannot be so hard. Making irregular flans cannot be so hard. None of us really want to think about this, but the genie seems to be out of the bottle on this list. I still believe that the great majority of coins on ebay etc are real, but this is all quite unsettling. Fakes entering the low end market is both plausible and disconcerting. Old pros, please shoot all this down, but lots of us are thinking this. Shall we start accepting only coins from dies which are reported in the literature older than 1980?!
From: David Welsh Date: Sat Feb 24, 2001 8:59am It is a LOT harder to make really deceptive fakes than you think. My definition of a "really deceptive fake" is one that can deceive an experienced numismatist most of the time. If an experienced numismatist becomes suspicious of a coin and starts doing die studies, the fake will almost always be uncovered. The problem is not that forgers know how to make fakes that are so good no one can detect them. The problem is that most collectors, and many dealers, simply do not know the material well enough to detect fakes that are relatively easy to recognize. Once a fake coin gets into a collection, particularly a prestigious collection, its chances of passing are greatly enhanced. If you don't know the material and buy a lot of coins on eBay, you are going to buy a certain proportion of fakes. The same is true of many other buying opportunities, such as dealer pick trays at coin shows. One of the nastiest ways fake coins enter the market is by being "salted" into hoard lots of genuine coins. No dealer has time enough to carefully examine every coin in a lot of 100 denarii that will be sold a specials or out of a pick tray, without attribution. The bottom line is that if you want assurance that the coins you buy are genuine, in one way or another you will have to pay for it - by learning the art yourself, or by buying high grade coins from dealers who know their material and from major auction houses. If you are concerned about the investment potential of your collection, that is the best strategy anyway. Don't be discouraged though, most of the ancient coins on eBay are genuine.
From: "Kenneth McCormick" Date: 2001 Feb 27, 5:43pm Subject: Cheap, beat-up forgeries I have heard it said that only relatively expensive coins in pretty good condition should be closely examined for authenticity. Daivid Sear says all AE's can be purchased with confidence. However, a very knowledgeable numismatist has told me he has seen forgeries that were so distressed that even if they had been authentic, they would have only been worth about $3. Also, I myself once bought a fake AE on eBay for $5 to $10. This was a rather attractive fantasy piece that the dealer was unwilling to unambiguously describe as such, suggesting instead that he did not know one way or the other. He thus lost my future business. I just wonder if anyone would be willing to comment on whether they have ever encountered very worn, inexpensive forgeries other than obvious tourist fakes.
From: Robert Kokotailo Date: 2001 Feb 28, 4:43pm Yes, they do exist. I have a number of them in my fake collection and will eventually publish them (generally Constantine and Licinius follii). They were made in Bulgaria to be mixed into un-cleaned lots to make the lots look better and bring up the over all price of the groups (you may pay more for a lot if you see a few interesting items peaking through the dirt). I have traveled in the Mid-east and had street venders in Egypt, Jordon and Turkey offer me coins for sale that were exactly the type of thing you are mentioning. They are not particularly dangerous if you now what to look for, but a beginner would be fooled by them. There is also a very well documented group of higher grade Constantine period bronzes (they are generally XF) which came out some years ago and are being handled by a dealer in the US well know for fake antiquities and coins. They are relatively convincing and would not be obvious from a average image, and even in the hand one has to look fairly close.