Detecting Counterfeits column from Aug. 8, 2016, Weekly issue of Coin World:
The counterfeit 1906 Coronet gold $5 half eagle illustrated here is a typical gold fake. The quality of this counterfeit is good, but this type of fake is not extremely deceptive once you know what to look for.
While the piece exhibits no obvious patches of tool marks or large repeating depressions on the coin, other diagnostics can be used to detect this fake and most of its “cousins.”
The weight and gold content of this style of counterfeit is a good news/bad news situation.
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They are almost always the correct weight, diameter and thickness, and contain the same amount of gold as a genuine coin. This means that using measurements will do you no good when determining authenticity (the bad news), but if you get stuck with one of these $5 counterfeits, you at least end up with approximately one-quarter ounce of gold (the good news).
This fake was produced by transferring the details from a genuine 1906 half eagle to a set of counterfeit dies. The genuine model coin most likely graded About Uncirculated 53.
We know this by inspecting the high points of the counterfeit — there is a minor loss of details on all the high points, even though the counterfeit is fully lustrous.
This is a good diagnostic for all U.S. gold — if the coin has the luster and surfaces of a Mint State example, but the high point detail of an Extremely Fine to AU coin, you should take a closer, much more critical look.
Other things to look for on this type of counterfeit are unusual color and luster; tiny raised lumps on the devices and in the fields, especially where the fields meet the raised devices; and an overall loss of finer details.