A “super rare” 50p coin has sold for a whopping £4,500 in Wiltshire because of an unusual error.

The Britannia Coin Company, based in Royal Wootton Bassett, sold the coin to a private collector after it was authenticated by The Numismatic Guarantee Company.

The valuable coin is a rare mint error Gibraltar 50p that has a portrait of the late Queen Elizabeth II on the heads side, along with the date 1990.

On the other side of the coin is a Christmas-themed design showing a choir boy and a puppy.

This chorister design is usually seen on 1989-dated coins, meaning that the heads and tails sides are mismatched.

Coins with mistakes like these are known as ‘mules’, and this one was discovered by a private seller who asked the Wiltshire firm to sell it on their behalf.

The £4,500 fee collected for the 50p makes it much more valuable than the 2009 Kew Gardens 50p, a well-known rare coin that often sells for around £250 online today.

Experts at The Britannia Coin Company have urged people to check their spare change, as there is likely to be more of this particular “error” coin in circulation.

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Christopher Collects with the rare coinChristopher Collects with the rare coin (Image: The Britannia Coin Company)

“These non-UK 50ps are already rarer than the ones we are used to seeing in our change,” said Christopher Collects, a coin expert and YouTuber who works for The Britannia Coin Company.

“As this is the only example of this particular manufacturing mistake that has been found so far, this coin is one of the rarest modern coins out there.

“Since the error has only just been discovered, nobody has been looking for it, so there could definitely be more.”

The coin was so rare that Christopher was concerned it may have been a fake.

But it has now been authenticated and can be found in The Numismatic Guarantee Company’s online register of authenticated coins.

Christopher added: “I was worried this coin was a fake, so I got a second opinion from the experts at the Numismatic Guaranty Company.

“They are specialists in rare coins and authenticated the Gibraltar 50p as a real mint error.

“That’s why it's in a protective case with a unique reference number, because it was added to their database.”

Other examples of mint error coins where a problem occurred in the manufacturing process are undated 20ps.

In 2008, The Royal Mint released about 250,000 20ps into circulation without a date on the coin.

Today, these error coins can sell for more than £100.