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How do collectors and experts detect forged coins?

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Ancient Roman coin — coin collecting Obverse of a silver denarius showing the mythical hero Aeneas.

In the context of coin collecting, experts and authorities identify forged coins by examining their manufacturing characteristics, as counterfeits are frequently produced using different methods than genuine currency.

While genuine government-issued coins are typically struck using high-pressure machinery, counterfeiters often rely on casting to replicate the appearance of a coin. Because casting is a less precise process, forged coins often exhibit specific telltale signs, including:1

Lack of definition: The details on the coin may appear soft or blurred compared to the sharp, crisp imagery found on genuine struck coins.1
Surface irregularities: Counterfeiters often leave behind tiny globules of metal, which occur when molten material penetrates the porous areas of a mold.1
Plating issues: Forged coins may show signs of thin or uneven plating.1

Historically, the difficulty of replicating official production techniques—such as the unique marks left by a punch or the specific weight and composition of the metal—has served as a primary defense against counterfeiting. Close inspection of these physical features remains the most reliable method for distinguishing authentic pieces from fraudulent imitations.21