One of the greatest – or most infamous, depending on how you look at it – errors in numismatic history involves the 2000 Sacagawea coin.
If you’re not familiar with the term “mule”, a mule error is the production of two different coin designs on one coin. Prior to 2000, no U.S. coins had a mule error, but the Sacagawea coin broke that streak.
The coin was accidentally printed with the obverse design of a U.S. State quarter along with a Sacagawea reverse of an eagle.
After discovering the error, the Mint found thousands of coins with the same error at the Philadelphia Mint. These coins were melted to avoid any problems.
The question also arose whether the mule error coin could be legally owned. After all, if a coin is a partial quarter and a partial dollar, what denomination is it really?
Debates erupted on how this could have happened, and the Mint reported that it was due to the same size die of the State Quarter and Sacagawea dollar.
As it turns out, the mule error was produced three different times. Rogue employees probably were to blame for the printings. Two employees were also caught selling the coins for profit. The former employees received fines and jail time.
While the Mint destroyed most of the mule error coins, ten known coins still exist. One estimate says that a single Sacagawea Mule would bring in as high as $250,000 at auction.