Mint Error Coin Chronicles: Dual Obverse and Dual Reverse Mules
Posted on 4/15/2025
Numismatic Guaranty Company® (NGC®) is the world’s leading authority on mint errors, a popular segment of numismatics. In Mint Error Coin Chronicles, we take an in-depth look at a specific kind of mint error. This month’s topic is Dual Obverse and Dual Reverse Mules.
Even coin collectors at the start of their numismatic journey are familiar with the concept of a two-headed coin, which is famous for being part of a trick to always correctly call a coin flip. Comic book fans are likely familiar with Batman villain Harvey Dent's two-headed coin, typically shown as a silver dollar. The US Mint actually issued a two-headed coin over a century ago: the 1904 Lewis and Clark Commemorative Gold Dollar, which includes busts of each famous explorer: Clark on one side and Lewis on the other.
One error that gives the appearance of a two-headed coin is a Brockage, in which a newly struck coin does not eject properly from the minting equipment. In this case, when a new planchet is inserted between the dies, the obverse of the stuck coin can impart an inverse image of its design to the reverse of the next coin. But with a Dual Obverse Mule, the strike comes from two obverse dies that were incorrectly matched together. An example is this France 1657 Liard, which has a portrait of King Louis XIV on each side, with each king looking to the right, as expected. (This coin is part of a Heritage Auctions sale in April 2025.)
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The equivalent error with the reverse side of the coin is called the Dual Reverse Mule. This Netherlands 1754 West Friesland Duit is part of a Heritage Auctions sale in June 2025.
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