A mule error occurs when a coin is struck using two dies that were never intended to be paired together. This can involve dies from different denominations, different coin series, or even different countries. Mule errors are among the rarest and most valuable mint errors, as safeguards are in place to prevent mismatched die pairings.
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Scan My CoinA coin struck with obverse and reverse dies from two different denominations, such as a quarter obverse paired with a dollar reverse.
How to check: The two sides of the coin will show designs from different denominations. The coin's size and weight may match one denomination but show the design of another.
$50,000 - $100,000+Dies from different coin series accidentally paired together, such as a regular-issue obverse with a commemorative reverse.
How to check: One side shows a standard design while the other shows a design from a different series or program.
$10,000 - $50,000+Dies from coins of different countries paired together, typically at mints that produce coins for multiple nations.
How to check: The obverse shows one country's design while the reverse shows another's. This is more common with foreign coins produced at contracted mints.
$5,000 - $25,000+A coin that was first struck as one denomination, then struck again with dies for a different denomination, showing elements of both.
How to check: Both designs will be visible, with the second strike overlapping the first. The coin may show two different denominations.
$1,000 - $10,000+A mule coin is struck using two dies that were never intended to be used together. This includes dies from different denominations, series, or even countries. They are extremely rare because mints have safeguards to prevent mismatched die pairings.
Mule errors are among the most valuable mint errors. The 2000 Sacagawea dollar/Washington quarter mule has sold for over $100,000. Values depend on the rarity and desirability of the specific die combination.
Mule coins occur when a mint worker accidentally installs the wrong die in one of the die positions. This is extremely rare in modern minting due to computerized die management and different die sizes, but it still occasionally happens.
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