Australians have been urged to check their $1 coins, as some of the rarer ones could be worth a staggering $3,000 

A sharp-eyed coin expert has revealed that a tiny error made by the Royal Australian Mint in the production of a batch of common coins has increased their value by 3000 times.

Perth-based numismatist - a fancy name for a coin collector - Joel Kandiah said 'astonishingly this error went unnoticed for a year or two.'

He revealed the flaw on his popular thehistoryofmoney TikTok account.

'A batch of $1 dollar coins from the year 2000 had been mistakenly produced using the incorrect obverse die (the heads side) and subsequently entered circulation,' he said.

The mint used the 'heads' template meant for 10c coins instead of for $1 coins, which meant the raised part of the coin which should be on the edge is instead slightly inside, creating a double rim.

'The different between a regular $1 and the 'mule' coins is that the latter has a 'pronounced double rim around the obverse of the coin',' Mr Kandiah said.

Given the 1.4-millimetre difference in diameter between the 10 cent and $1 coin, the mistake led to the creation of the 'legendary 2000 $1 'mule' coin'.

Because the value of a coin is principally determined by its scarcity, these $1 coins could be worth plenty.

'If you happen to discover one of these rare mules in your change, they can be valued between $300 and $3,000, depending on their condition,' Mr Kandiah said.