An extremely rare coin that is no longer accepted in shops is set to sell for hundreds in Wiltshire.

The 25p coin looks like an ordinary 20p in terms of shape, but features a shield on one side with the word 'experimental coin' and the Sovereign’s Orb on the other.

This is because the coin was only produced very briefly as a short-lived experiment.

It is thought to have been made by skilled craftsmen at the UK’s Royal Mint before the denomination was officially released into circulation in 1982.

At the time, authorities had not even decided whether the coin would be worth 20p or 25p.

But one Wiltshire man, who is not a coin collector, had his lucky day when he was handed the rare 25p coin in his change several years ago.

Only 50 of these coins were ever producedOnly 50 of these coins were ever produced (Image: RWB Auctions) After hanging on to it for some time, the man was informed by experts at RWB Auctions, which has a track record for selling the rarest UK error coins, that the coin was likely to see for between £500 and £700.

It will now go under the hammer in Royal Wootton Bassett on Wednesday, September 25 as part of a specialist sale of historic and modern currency.

It has been estimated that no more than 50 of these 25p trial pieces survive in the world, making it significantly rarer than the famous Kew Gardens 50p, of which 210,000 were made.

“This is a fascinating piece not just for the rarity but as a glimpse of what our currency could have been," said Youtuber Christopher Collects, who works as a coin expert for RWB Auctions.

"20p coins are a fixture in our change now, but the Royal Mint seems to have experimented with various ideas before they settled on the seven-sided coin we all recognise.

The coin will go under the hammer at RWB AuctionsThe coin will go under the hammer at RWB Auctions (Image: Dave Cox) “Trial pieces are best thought of as experimental coins minted to see if they would work in circulation.

"They would have been used to demonstrate the concept of a new coin to officials and may have been sent out to businesses that handle lots of cash to try out. Think of companies that make vending machines or operate parking meters.

“This trial coin could easily be mistaken for a 20p, but we are certain it will sell for a lot more than that.

"While there are not many of these experimental 25p pieces out there, it's worth checking your change to ensure you haven’t been handed a rare and valuable coin!”