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Stereomicroscope a necessary tool

Over the years, I have seen dealers and collectors use many methods to authenticate coins.  Sometimes they work.  Nevertheless, I have found that the most reliable method is simple examination using a stereomicroscope.

This article was originally printed in the latest issue of Numismatic News.
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Over the years, I have seen dealers and collectors use many methods to authenticate coins. Sometimes they work. Nevertheless, I have found that the most reliable method is simple examination using a stereomicroscope.


In my last column, I mentioned that Brian Silliman and I taught one of the counterfeit detection classes at this year’s American Numismatic Association Summer Seminar. In the class, we teach students to first look at a coin with their naked eyes in order to form a “gut reaction” regarding its authenticity. For a beginner, forming a first impression is difficult because they usually have no prior experience to draw from. Those students who are longtime collectors or dealers usually do better as they have looked at thousands of genuine coins. After a cursory exam, the students use a stereomicroscope to look for characteristics found on genuine or counterfeit coins.

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With or without access to a microscope, I have seen people toss a specimen on a desk to check the sound it makes when it lands. Many will also balance the coin on their fingertip and tap its edge to listen for the tone of its ring. Unfortunately, in order for a “ring” test to be useful, you’ll need to train your ears by ringing hundreds of genuine coins. Anyway, in my experience, most fakes that have an odd ring can be detected by simple observation. I’ve even seen people bite a coin. Sometimes each of these methods may provide a clue or at least back-up an initial finding about a coin’s authenticity, but they should be secondary.

This summer, I saw a dealer trying to spin an Indian $5 gold coin in order to test its authenticity. I became aware of this fad sometime in the late 1970s. Actually, some counterfeit Indian half eagles do spin. Unfortunately, some don’t. By experiment, I learned that some genuine coins also spin, so what’s the point? When I saw the student trying to spin the coin, I suggested that he put it under his microscope first in order to look for some of the characteristics found on counterfeits that we had discussed in class. Why risk the chance of marring a genuine specimen with circular hairlines due to grit rubbing its surface while trying to make it spin?

After examining coins using a stereomicroscope, you become thoroughly familiar with most surface characteristics found on both genuine and counterfeit coins. That is why we teach authentication classes using microscopes. Look at the 20X micrograph of the arrow tips found on the reverse of a Morgan dollar. What is the brown speck? I have to keep myself from laughing sometimes as I listen to numismatists try to explain marks such as this. Wild theories abound because they are not viewing the coin as close as you are seeing it here. In one instance I heard a seasoned professional numismatist tell her group that this type of mark was a carbon spot. In actuality, this is a piece of sawdust used to dry the planchets at the Mint over a hundred years ago. It remained on the planchet and was struck into the coin.

One of the most unusual efforts at authentication that I have ever witnessed occurred with a Morgan silver dollar. An experienced professional spent about 15 minutes trying to prove a semi-key dollar was altered by using diagnostics for genuine specimens found in the Comprehensive Catalog and Encyclopedia of Morgan & Peace Dollars by Van Allen and Mallis (VAMs). He finally declared that although the coin had many attributes that were characteristic for a genuine coin of that date and mint, it was not a perfect match so it must be altered. He was correct. When I got to view the coin, it took less than 10 seconds to detect a large gap at one side of the mintmark where it didn’t touch the field.

Finally, don’t let yourself get bogged down with unnecessary research. A few decades ago the unique 1870-S half dime was sent to us for authentication. The Seated Liberty experts were of divided opinions as to its authenticity. Everyone wanted the coin authenticated. Perhaps it was the dark blue-steel color of the coin or the weakness of the “S” mintmark that caused concern. Perhaps it was the fact that the coin was unique. I do remember that Charles Hoskins, the director of the service and myself determined that the coin was absolutely genuine by simple observation using a stereomicroscope in less time than it took you to read this far. Then we backed up our findings with a specific gravity test. Later that same day, Charlie took the coin over to the Treasury Department’s Mint laboratory so they would have the pleasure of viewing this unique coin using their microscope.

If you get the chance to view coins using a stereo scope it will open a whole new world to you. Otherwise, you’ll have to let the professional authenticators at the major grading services have all the fun.

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