Many of the more dangerous modern fakes of ancient coins are die-struck, as this is the only way to create the look and feel of an original die-struck coin, the lack of which is one of the keys to spotting other types of fakes. Fortunately that look and feel are not enough to allow a fake coin to pass as genuine, as there are major technical problems in creating false dies. Accurately capturing the image, artistic style, striking characteristics, and microscopic details of a genuine ancient coin is not a simple thing. Many forgers have come close, but virtually all have made at least one fatal mistake that allows their fakes to be detected.
There are a number of ways to produce dies, most of which are a variation on one of the following :
Pertinax fake from hand cut die
False hand-cut dies can produce some the most dangerous fakes, but only when cut by a very talented technical engraver. Such engravers are few and far between, and can make a very good living without resorting to criminal activity. Most of the engravers attempting to cut dies are artists and so are doomed to failure because of the nature of artistic training and the artistic mind. In order to cut a die that will strike coins that will pass as genuine, the diecutter must deal with all of the following problems:
1) THE IMAGE - The basic image on an ancient coin is relatively easy to capture by either an artistic or technical engraver. It is just a matter of looking at the original coin, and copying in negative what one sees in positive. But it is not enough.
2) ARTISTIC STYLE - Art is not a process of exact duplication but rather of interpretation, in part controlled by the subconcious mind. This is a difficult concept to explain, but it results in every artist having a unique style that is recongnizably his and no one else's. This was true of the ancient celators cutting dies 2000 years ago, and is still true for a modern one cutting forgers' dies today. Capturing the image on a coin might fool a novice collector, but once he learns enough about artistic styles and how to recognize them, he will be able to look at a coin and determine if the unique style of that die is correct for one of the ancient celators who worked on that particular series of coins (seldom more than 2 or 3 celators worked on any given issue of coins), or it is the style of SOMEONE ELSE not known to have worked on that series. If it is someone else, it has to be the work of either an ancient counterfeiter, or a modern forger (and those distinctions have to be made in other ways).
A handful of forgers have on occasion come very close to a convincing style for one or two types. Carl Becker, probably the best technical engraver of forged dies, attempted dies for about three hundreds types of ancient and medieval coins, but even he only got two or three of them close enough to be really successful, with his facing bust of Postumus example (illustrated on the introduction page) being one of the better ones.
3) THE FINE DETAILS - A genuine ancient coin, struck from genuine ancient dies, is not an exact replica of what was engraved on the ancient dies. During striking, metal flows into the dies to transfer the image to the flan, but there is always some degree of distortion and/or incomplete transfer. Sometimes the metal does not fully fill the die and some parts of the coin will end up flatly struck. When the pressure forcing metal into the dies is released, it can rebound slightly resulting in lines that can be either thicker or thinner than those engraved into the die. If the die was not perfectly vertical, one edge of the coin will receive a strong strike and the other side a weak one. Some coins get slight double strikes. In fact most ancient coins will show more than one of these features. As a result, even if a modern diecutter cut a die that perfectly copied such a coin, it would not perfectly copy the die that coin was struck from and thus could not be be used to strike perfect fakes.
4) THE MICROSCOPIC DETAILS - As a die is cut, the tools used leave microscopic marks that to some degree are transferred to a coin struck from that die and become part of the coin's surface texture. To reproduce these marks the forger must cut his dies with the same tools and methods used by the ancient celators, except today we know almost nothing about ancient die cutting techniques, making copying them rather difficult. Modern die cutters normally use modern tools and techniques, so the microscopic details of such dies (and the coins struck from them) are different than on ancient coins. To examine these marks on the coins will require a very good microscope looking at a fairly high grade coins. This is normally beyond the ability of the average collector, but such microscopes are available. Even without a microcope, these marks affect how light reflects off a coin, which is why many modern fakes "look wrong" even when the image looks right. Of course, this will not help one much on highly worn or overcleaned coins where the original surface textures are no longer present.
Even if a diecutter were to do everything right and cut a prefect die, he would still have to determine how the original flans for that exact issue of coins were made, and perfectly duplicate the hand striking process (most modern forgers use hydraulic presses and get a result that is easy to detect as such). So we can see, there are so many details a forger would have to get right to make a perfect forgery, and so many places he can go wrong, that perfect, non-detectable hand-cut die forgeries are virtually impossible. Good ones do exist so one must look very closely to spot them, but they can always be spotted if one has enough experience.
What keeps the average collector safe from the few really good forgers cutting fairly convincing hand-cut dies, is that such forgers cannot afford to waste effort on inexpensive types. If any one type suddenly shows up with hundreds or thousands of high-quality coins from one set of dies (or even a small number of different dies), alarm bells start ringing and the coins are placed under even closer scrutiny and will likely be condemned fairly quickly. This happened with the "Black Sea forgeries" and the "New York hoard of Apollonia Pontica" forgeries a few years ago (both of which have links on the links page). Such forgers must spend many hours perfecting a single set of dies with which they can make one or two coins they can sell for tens or even hundreds of thousands of dollars, and then never use those dies again. The average collector will not be exposed to such coins, so need not worry about them.
These dies were found in a flea market in Spain some time between 2000 and 2003, and there is no doubt that they are modern forger's dies (the image was provided by Mr. Ramon from Spain, and used with his permission). They copy a gold aureius of Julius Caesar and while the obverse is very poorly done, the reverse is a little better and slightly convincing if you are not looking too closely (click here for a modified image that shows the coin as a positive). This is a case where the basic image was captured (although badly on the obverse) but the artistic style does not even begin to resemble that of a genuine coin of the type. I have not yet seen a coin from these dies offered for sale, most likely because once the forger had cut them he realized they were so bad that there was no possibility of passing coins struck from them.
Mechanically Cut Dies
There are machines which will trace the surfaces of a genuine coin and guide another machine in cutting a negative image of that coin into a new die. The advantage of these machines is that they eliminate the artistic interprative process that plagues people hand cutting dies. They allow them to almost perfectly capture the image and style of the original coin, but there are several problems they cannot overcome :
1) As discussed in section 3 above, genuine ancient coins are not perfect copies of the ancient dies they were struck from. The same small differences that apply to hand-cut forgers' dies apply to copying machines. It is probably even worse, because a human might be able to compensate for them to some degree. A machine cannot.
2) As discussed above in section 4, the ancient tools used to cut ancient dies leave microscopic details on genuine ancient coins that cannot be duplicated by a modern copying machine. This is a major obstacle for such forgers.
3) The machines that trace the original coin can only do so in a set pattern with a set spacing. There is no way this can capture all the really fine details that hand cutting creates, and this minor loss of detail creates a die that results in a coin that has a slightly "soft" lookover all.
The end result is that coins struck from mechanically reproduced dies will never be great fakes that will fool true experts, but they can be fairly dangerous to more novice dealers and collectors, or experts that are not looking closely. Such dies can be relatively cheap and easy to make, which makes this one of the more common methods of choice for modern forgers. With enough experience, one can learn to recognize such fakes, but a good microscope is a necessary tool.
One thing forgers can do to improve such dies is to touch up some details by hand engraving on the die to get rid of that "soft" look. This is difficult to do well, and has its own problems as one can see on the coin illustrated (and the close up below) :
The original coin was probably somewhat worn, resulting in a die designed to strike coins already looking slightly worn. If you look closely at the very back of the head there is an area of hair that is crisp and sharp, with no wear. Ask yourself how a coin with this much wear fairly evenly across the coin, has such an area with no wear on it. This is inconsistent with a coin worn in circulation. The reason that area has no wear is that there is actually little if any wear on this coin. The parts that look worn were that way on the die, and the re-engraved parts of the die looked sharp on the die and remain that way on the coin. There is also something about the portrait that just doesn't ring true, which results from how a die-cut to copy a coin does not capture what was actually on the original die, and thus cannot accurately strike coins that reproduce what was on that die.
Spark Erosion and Impressed Dies
(and dies made by related processes)
There are a number of ways by which dies can be produced by non-mechanical methods.
1) A process called "spark erosion" has been around a long time, where coin is placed next to a blank metal die, and electric sparks are passed between them which erode away the disk at their points of closest contact. Gradually an impression of the coin will be formed on the surface of the disk (see this link to a dental lab where it is used for more details).
2) Impacting a genuine coin into a substance the same hardness, or softer than the coin, can capture the image. If you want to preserve the original coin you must use a substance significantly softer than the coin and then hardened it to make a useful die. The process is no different than that which results in the many ancient brockage errors we see, and the technique was sometimes used in ancient times by ancient counterfeiters. Today there are high-tech plastics that start out soft enough to take the impression of even a gold coin without harming the coin, and which after hardening are strong enough to strike a few coins with. As new materials and technologies develop, new methods are constantly evolving, so we cannot even begin to discuss all the possibilities.
Although such dies can sometimes fairly accurately capture the designs and style of the coin being copied, as discussed previously that die is not going to be an accurate copy of the ancient die that coin was struck with, and the differences can be spotted with enough experience. Add to this that there is almost always some minor loss of details, resulting in a slightly "soft" looking coin. Some modern technical advances have in part reduced the problems, but we prefer not to go into those details so as not to give ideas to the wrong people. In any case, while they have reduced the problems, they have not eliminated them.
In the end, there are no perfect modern dies.
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