The medal was donated to the Great Centenary Charity Auction after it was left in an envelope marked for the attention of the Royal British Legion.

It is one of around 200 made as spares for the Games as, unlike medals given to winning athletes, it does not have an engraving around its rim displaying the winning discipline.

"Not all of the medals made were engraved," a spokesperson for the Royal Mint, which manufactured medals for the London 2012 Olympic and Paralympic Games, said.

"The medals given to the athletes were, but around 200 were made as spares.

"The remaining medals were returned to the Organising Committee of the Olympic Games.

"We do not know what happened to them after that."

Auctioneer David James still believes the medal can make a reasonable sum of money at the event, which is being held at Raynham Hall, Norfolk, next September to raise money for research to help bomb blast victims.

"It must be extremely rare, so should still be quite valuable," he told the Eastern Daily Press.

He added that the medal is the most intriguing item he has come across in his 50 years in the business.

"I was amazed to receive such a treasured medal although I had read that an athlete had given his medal to a charity shop some months ago," he explained.

More information about the auction can be found here. 

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