Did U.S. Mint put secret marks on its coins?

Up until a few years ago, most of my working day consisted of examining coins using a stereo microscope. Many things I saw have not been shared publicly as there was confirmation that counterfeiters were using authentication information to improve their fakes. There was much to discover and record as the microscope expanded what we could see. For instance, would you believe that Mint engravers put “secret marks” on many hubs and dies to deter counterfeiters? I do. It would be interesting to be able to go back in time and learn about this practice. Perhaps some researcher of the Mint archives could verify this as fact. For now, let me make my case.

When authenticators check a coin’s authenticity, one technique is to look for repeating marks or defects. That works great on two identical fakes, but counterfeits in a series can have several different dates. Fortunately, when the plague of counterfeit gold coins began to hit the U.S. market in the late 1960s they were not very sophisticated by today’s standards. In many cases, fake coins bearing different dates were all struck with the same reverse. There are many cases of genuine coins being struck from dies carried over from a previous year. Many genuine coins also have the same “markers” over several years due to the fact that the characteristic is found on the hub and was transferred to the working dies. Nevertheless, when a defect (not on a hub) appears on a coin from the 1870s and is seen on coins dated 1902 and several dates in between; that is a clincher that something is amiss. The first example of repeating defects I was shown occurred in the Liberty $2.50 series where a patch of rust lumps above and to the left of the eagle’s beak was present on counterfeits bearing many different dates.

That brings me back to the “secret marks” placed on coins. The reason I’ll call them secret marks is when I first discovered them, I was reminded of the secret marks applied to the designs of postage stamps in the 1870s by the various bank note printing companies to identify their production. These marks consisted of extra lines, dots, etc., hidden in the design of the stamp. I thought perhaps the Mint did the same thing. There was one glaring problem with my theory. Coins were produced in this country and the world long before the first postage stamps were conceived. Additionally, mints of the world used mintmarks to identify the facility where the coins were made. So what use were the secret marks I was finding on coins? They must have been a deterrent to counterfeiting.

Fig. 1 shows an 1813 gold $5. Note that the star point closest to the rim has a notch. I call this a “broken 13th star.” This “defect” is seen on too many coins to be random. A quick look on the edge of some $10 Indians (Figure 2) and $20 Saints (Fig. 3) will show that this broken star marker has been carried over for at least a century.

At one time, this would be a good deterrent to counterfeiting. In the old days, if a coin had stars, the faker would engrave a star. He wouldn’t think of leaving one incomplete. By the mid 1970s, the techniques used to make false dies by transfer methods far surpassed any deterrent that a secret mark would provide. Today, it is best to send suspect coins to a grading service for authentication.

Now I have a challenge for you. There are many more secret marks such as the broken star on our coinage. Perhaps the easiest to discover occurs on Liberty half eagles near the turn of the century. Hint: there are two of them in the denticals around the obverse rim. After you’ve had some time to look, I’ll show a micrograph of the marks in a
future column.