The salmon 50p, which entered circulation in 2023, has been listed by a seller from Droitwich Spa, Worcestershire, for £93.24, almost 200 times its value.
According to the Royal Mint, the King Charles Salmon 50p is the rarest 50p in circulation, with less than 200,000 minted.
A spokesperson for the Royal Mint said: “Part of eight new definitive designs representing flora and fauna from across all four UK nations following His Majesty King Charles III’s ascension to the throne.
“Although wild populations of the Atlantic salmon are affected by factors such as river pollution, habitat loss, overfishing, and river heating due to lack of tree cover and climate change, this wild fish can be found in very clean rivers in Scotland and Wales, as well as in north and south west England.”