A medieval chess piece kept in a drawer of an Edinburgh home could sell for £1m at an auction taking place on Tuesday.
Its owners had no idea that the object was one of the long-lost Lewis Chessmen.
The chessmen were found buried in a sand dune on the Isle of Lewis in 1831 but the whereabouts of five pieces have remained a mystery.
The Edinburgh family’s grandfather, an antiques dealer, had bought the chess piece for £5 in 1964.
He had no idea of the significance of the 8.8cm piece (3.5in), made from walrus ivory, which he passed down to his family.
They have looked after it for 55 years without realising its importance, before taking it to Sotheby’s auction house in London where it is due to be auctioned.
The Lewis Chessmen are among the biggest draws at the British Museum and the National Museum of Scotland in Edinburgh.
Made in Scandinavia, possibly Norway, they are seen as an “important symbol of European civilisation”.
Sotheby’s expert Alexander Kader, who examined the piece for the family, said his “jaw dropped” when he realised what they had in their possession.
Despite not knowing its significance, the late 12th/early 13th Century chess piece had been “treasured” by the family.
The current owner’s late mother believed it “almost had magical qualities”.
The Lewis Chessmen set includes seated kings and queens, bishops, knights and standing warders and pawns.
Some 82 pieces are now in the British Museum and 11 pieces held by the National Museum of Scotland. As well as the chess pieces, the hoard includes 14 “tablemen” gaming pieces and a buckle.
Since the hoard was uncovered in 1831, one knight and four warders have been missing from the four combined chess sets.
The newly-discovered piece is a warder, a man with helmet, shield and sword and the equivalent of a rook on a modern chess board, which “has immense character and power”.
The discovery of the hoard remains shrouded in mystery, with stories of it being dug up by cattle grazing on the dunes.
It is thought it was buried shortly after the objects were made, possibly by a merchant to avoid taxes after being shipwrecked, and so remained underground for 500 years.