Twenty-two years after its production at the Denver Mint, the only known example of a double-denomination mule error coin featuring a Sacagawea dollar obverse and the reverse of a South Carolina State quarter dollar has been authenticated and certified as genuine by Professional Coin Grading Service.

PCGS graded the mule coin as Mint State 64.

A mule is a coin struck with obverse and reverse dies not intended to be paired together. For this error, illustrated nearby, a reverse die intended for use in striking South Carolina quarter dollars was paired with a Sacagawea dollar obverse die in a coinage press dedicated for dollar coin output.

The grading service shipped the coin to error coin specialist Fred Weinberg for his professional opinion.

Weinberg confirmed to Coin World June 8 that the coin was struck on a dollar coin planchet weighing 8.1 grams, the standard for the dollar coins, and measuring 26.5 millimeters, with a plain edge.

The Sacagawea dollar has a manganese-brass clad composition, comprising outer layers of 77% copper, 12% zinc, 7% manganese and 4% nickel bonded to a pure copper core.

Weinberg said he saw no evidence that would suggest the mule error was made from two separate coins united into one.

Weinberg said that, since the diameter of the quarter dollar die is smaller than that of the dollar planchet, the strike resulting from the quarter dollar die would exhibit the appearance of a double rim.

Other U.S. mules that have been authenticated include: the first identified, featuring an obverse of a State quarter dollar and the reverse of the Sacagawea dollar, struck on the golden dollar planchet; a mule with a Sacagawea dollar obverse and Presidential dollar reverse, also struck on a golden dollar planchet; a mule error struck with two Roosevelt dime reverse dies on a copper-nickel clad dime planchet; two examples of Washington quarter dollar mules from two reverse dies, presumably struck at the San Francisco Mint circa 1965 to 1966; a unique 1993-D piece struck on a cent planchet with a Lincoln cent obverse die and Roosevelt dime reverse die; and a 1995 piece struck on a dime planchet by a Lincoln cent obverse die and Roosevelt dime reverse die.

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