The blemished piece of change, which was minted in 1990, had been created for a British overseas territory before being pulled from circulation due to its poor quality. The coin - which was struck in copper-plated steel blank - sold on Wednesday (Aug 9) for its hefty price tag at Tennants Auctioneers, in Harrogate.

Collector Alun Barker is understood to have picked up the one-of-a-kind piece on Ebay in December 2017 for just £50. And a few months later, in January 2018, the coin was confirmed as genuine by the Royal Mint, who provided it with a letter of accreditation. Specialists Tennants had expected the disfigured money to reach at least £1,200 when it went under the hammer.

The sale also included several other impressive pieces of currency, including a George VI, 'Coronation' gold proof set, from 1937, which sold for £11,000. The four coins collection included a £5, double sovereign, sovereign and half sovereign. And they bare the monarch's head as well as a relief of George and the dragon, which was created by Italian engraver Benedetto Pistrucci.

This 1990 20p has been struck on a copper-plated steel blank intended for one of the other countries the Royal Mint produces coins for; a spectacular error and the only one of its kind known, on discovery the coin was featured in the national press

The set came in a Royal Mint red leather case with a GRVI monogram - the King's royal cypher - and the words 'specimen coins 1937' in gilt lettering. It was just one of 5,001 that were created. The sale also included a rare Pattern Crown coin from 1966, which was designed by Anthony Foley and struck in.925 silver, which sold for £2,300.

It was just one of only 100 struck bears the conjoined busts of Elizabeth and Phillip along with the warrior Britannia riding in a chariot while hurling thunderbolts.

A Charles III four-coin gold proof set, minted in 2022 to mark Queen Elizabeth II passing, also sold for £1,400 It comprised a double sovereign, sovereign, half sovereign and quarter sovereign and was one of only 750 sets.

The coins were housed in a Royal Mint box of issue with an accompanying booklet and certificate of authenticity. Included in the same lot were a 1699 cheque complete with seal and an interesting £20 error note with misaligned colours. Following the sale, Tennants Auctioneers' Coin Cataloguer Will Dobbins said he was impressed with how well the money had sold.

He said: "This was a really good sale overall, selling 98% of the lots offered, and we were delighted to achieve such strong results for our vendors. Of particular interest was a 1966 Pattern Crown. Minted in sterling silver, it was designed by Anthony Foley and was one of only 100 struck.

"This pattern features the conjoined busts of Prince Phillip and Queen Elizabeth II, with a striking image of Britannia hurling thunderbolts on the reverse. It exceeded the presale estimate of £1,000-1,500 to achieve a hammer price of £2,300."

Rare 20p coin with 'spectacular error' bought by Yorkshire collector fetches £1,400 at auction