The "double-header" was minted accidently in 2007 and is considered rare and valuable among keen numismatists.

"[The coin is] very hard to come across because the mint processes are so stringent now, to find error coins in this day and age is incredible," The History of Money's Joel Kandiah said in video posted to social media.

One of these coins sold on eBay for $1,900 in July, 2023. Another is listed for $4,999 but remains unsold.

A seller said "the Australian 2007 5c piece double-sided obverse coin strike is one of the rarest and most collectible coins since the 1930 Australian penny".

Coin collectors are advised to keep an eagle eye because "less than a few hundred are thought to have been circulated".

IN OTHER NEWS: