Coins with Surface Problems among the Greatest Challenges to Authenticators

Posted by Skip Fazzari, Authentication Consultant to NGC, on 10/19/2007

Counterfeit and cleaned? Or the genuine thing? This problem requires an expert eye.

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Authenticators in the past relied heavily on a coin’s physical properties such as weight, diameter, thickness, color, and specific gravity to determine its authenticity. Today, our task has become more difficult. This is because counterfeits in general have become more sophisticated and deceptive. Many modern die-struck fakes are made within the tolerances of genuine Mint products, so measurements are of less help than they were in the past. At the same time, more “problem” coins are being sent to grading service providers.

Among the greatest challenges to coin authenticators are eighteenth and nineteenth century gold or silver type coins with no original surface remaining. The measurement of coins in this condition is seldom useful, due to the metal loss associated with them. Additionally, whizzed coins and coins that have been harshly cleaned, repaired, or recovered from the ground present special problems because, in many instances, they can look similar to counterfeits.

When a coin’s original surface has been ruined, most of the characteristics we use to authenticate are either changed or obliterated. Harsh cleaning can alter a coin enough so that its color becomes unnatural. Unusual color was once an indication of a poorly made fake. Cleaning also changes the color of any contact marks on a coin’s surface from bright to dull so that they resemble the marks transferred to counterfeits from a host coin. Coins recovered from sea water can lose parts of their design as well as traces of the metal flow lines that authenticators look for on coins struck from dies. Even repaired coins or coins that have been buried may develop smooth rounded lumps on their surfaces, similar to those found on cast replicas. In each of these cases, the microscopic appearance of a coin’s surface is lacking, making authentication difficult.

Collectors and dealers have the option to “walk away” from a coin that looks suspicious; yet professional authenticators are expected to know if a coin in any condition and with any surface problem is genuine or counterfeit. In cases where the original surface of a coin is lost, the expertise of a specialized numismatist or professional grading service is invaluable. Is it a century-old cast counterfeit that has been cleaned and whizzed or possibly a genuine coin that was unearthed and cleaned?

This article previously featured in Numismatic News.