Turning $1 into $3,000 sounds like a magic trick, but you could very well achieve it if you have a mule coin in your collection.

Without getting overly technical, there was an error at the Australian Mint in 2000, where a small batch of $1 coins were minted with the 10 cent obverse die (whatever that is), which created a 'double rim' affect.

Collectors are prepared to pay big money for these, some fetching up to $3000, so get digging through that coin stash.