This month’s counterfeit, a fake Indian Head gold $10 eagle, is an old “friend” of mine, one that I initially inspected back in 1981, during my first year with ANACS.

It is a rather deceptive fake that can be missed by many collectors, until you know what to look for.

While the coin has a number of counterfeit diagnostics, the easiest to spot are all on the date digits.

A series of horizontal “tool marks” can be seen on the lower half of each digit, strongest on the 9 and the first 1. Some additional tool marks appear on the rim, directly below the first 1.

Tool marks are tiny scratches on the surface of a die. They are caused by a sharp tool that cuts into the die, usually in an attempt to remove a raised defect, or strengthen die details.

These incuse scratches on a die produce identical raised lines on the coins struck from this die, and can be an excellent way to identify a fake coin.

These diagnostic tool marks are important because no genuine 1911 Indian Head gold $10 coins exhibit this pattern of tool marks on the date, only fakes.

Collectors considering the purchase of a 1911 gold eagle should always take a quick look at the date digits.

Keep in mind that while the presence of these tool marks is a guarantee that a given coin is a counterfeit, the absence of tool marks does not guarantee that the coin is genuine, as many other fakes of this date exist.

Michael Fahey is a senior numismatist at ANACS in Denver, Colo.