‘Mule’ is the numismatic term to describe a coin struck from dies not originally intended for use together. Australia’s most famous mule is a halfpenny struck in 1916. It is the rarest Commonwealth coin issued for circulation.
In 2000, a number of Australian dollar coins were mistakenly struck using a 10 cents obverse (heads) die. The 10 cents is marginally smaller than the dollar, which meant the resulting mule had a heavier than normal rim on the obverse.
Error coin collectors soon drove prices up and a scramble to find the rogue pieces ensued, particularly in Perth where many of the dollar/10 cents mules were released. Finds were subsequently reported in other parts of the country too.
Estimates vary considerably as to exactly how many were issued – perhaps 6,000 at most. Although highly unlikely to appear in change anymore, a 2000 mule dollar would make an exceptional find. A decent example could be worth up to several hundred dollars. The very best examples on the other hand have been known to command thousands!
Maybe it’s worth glancing over the next dollar coin you pull out of your pocket or purse?