An Olympic gold medal from the 2012 London games is to cross the block in a charity auction at James & Sons in Norfolk, UK.
The 2015 sale will raise funds for the Royal British Legion, although the medal's owner is something of a mystery.
The organisation reports that the medal was left at a valuation event in Suffolk in an envelope.
There is no engraving around the rim identifying the event that it was presented for, further compounding the puzzle.
The Legion has since put out an appeal for the consignor to come forward.
Auctioneer David James commented: "There is no information about whose medal it was or where it came from.
"Maybe it was a substitute or was given as a gift to an Olympic dignitary. I've no idea where to start in terms of valuing it."
Olympic medals have a strong collector base, particularly in the US, where the most desirable pieces can change hands for sums in the low to mid six-figure range.
Generic gold medals, such as the one offered at James & Sons, can achieve around $10,000.
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