By Michael Fazzari for Numismaster

One of the first things many authenticators look for on U.S. coins they examine is the presence of metal flow. This characteristic provides a good indication that the coin was made using dies. Forty or so years ago, this was virtually enough proof that a coin was genuine because at that time, most counterfeits were made by casting.

Even by the early 1970s, years after die-struck fakes had appeared, the majority of struck counterfeit coins showed little evidence of metal flow lines. In fact, most struck counterfeits of the day were similar to castings, having weak, mushy details.

It’s not that simple anymore. Authenticating a coin by metal flow alone is down-right ignorant. That’s because, over time, struck counterfeits began to show traces of flow lines, and even duplicated much of the die polishing lines found on genuine specimens. Today, there are many die-struck counterfeits that almost defy detection.

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