A 20p coin so rare that it is the only one experts have ever seen is set to fetch a whopping £1,800 at auction.
The coin was struck on a planchet - a plain metal disc - from a foreign country in 1990.
It should have produced using a bronze metal blank like all 20p coins made in that year.
The coin is believed to have been purchased on eBay for just £50 and it is now expected to fetch a whopping 36 times more than it was bought for.
It is also comes with a Royal Mint letter of accreditation.
Coin collector Alun Barker is believed to have purchased the ultra rare coin on eBay for £50 in December 2017.
It was listed as a 20p struck on a 1p coin planchet, but experts have confirmed its true metallic makeup.
In January 2018 the coin was verified as authentic by the Royal Mint, who have confirmed it as genuine coinage.
At the time of buying the coin, Alun, of Hull, East Yorks,. said he was 'over the moon' when he discovered how unique the coin is.
He said: "When I saw it I loved it straight away. I knew it was unique.
"It was fantastic to find out how unique it is. It's brilliant news. I was over the moon.
"I've been told that if I want to sell it I should put a reserve on it at auction for £2,200.
"When I took it to be valued they said 'the sky is the limit' because it's the only one.
"Everyone I've spoken to has never seen anything like it. I'm still taking it in. The magnitude of it is amazing."
The coin is being auctioned by Tennants Auctioneers in Leyburn, north Yorkshire on August 9.
A Tennants Auctioneers spokesperson said: "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.
"It's a spectacular error and the only one of its kind known."
A George VI 1937 Gold Proof set, which comprises of a £5, double sovereign, sovereign and half sovereign, will also be going to auction at the same time.
Only around 5,000 of the sets were minted and they are estimated to go for £10,000 to £12,000 at auction.
A 1966 Pattern Crown, which features a photo of Prince Phillip and Queen Elizabeth, will also be going under the hammer on August 9
It has a striking imagine of Britannia hurling thunderbolts on the reverse and is estimated to fetch £1,000 to £1,500.
