A mule is a coin struck from two dies that were not intended to be used together. Designs or denominations don't really figure into it but typically they are of different denominations. On the Liberty & Commerce mules mentioned earlier, the real question is what is a mule and what isn't. The Liberty & Commerce die was a stock die that was used on Conder tokens from several counties. Most were made by Peter Kempson and a few by William Lutwyche.
