A rare 50p coin created for the London 2012 Olympics has sold for £10,101 on eBay.

The coin, which depicts a swimmer as a representation of aquatic sports, is one of 29 competition-winning designs showing different Olympic and Paralympic sports.

Members of the public had been asked to send in their designs for each of the sports with the winning entries being immortalised in metal.

While the majority of the special edition coins are estimated at a value of around £750, the piece in question was particularly valuable as it had been printed in error.

The Royal Mint had redesigned the aquatic coin ahead of the release in 2011, removing some of the water in order to make the swimmer’s face clearer, but a few were printed with the wrong design and went into circulation before the realisaton was made.

It is unknown exactly how many of these are in existence but it is this rarity that makes them so valuable to collectors.

The seller found the coin while metal detecting on the beach and said that, despite not being an expert, they believed it to be genuine.

"I don't understand much about coins," they wrote, "but I believe this coin is genuine. Do not bid if you don't feel confident."

They initially put a £10 bidding value on the item but within 30 hours this had rocketed to £100 and after 10 days and 68 bids, the piece of history sold for the staggering £10,101.