A newly discovered medieval chess piece riddled with a history of equal parts fascination and mystery is set to head to auction later this summer. Bought for £5 by an Edinburgh antique dealer in the 1960s and having spent the last five decades stuffed in a dress drawer, Sotheby’s now estimates the 12th-century piece will bring in between £600,000 and £1 million ($760,000 and $1.26 million).

Carved from walrus ivory, the piece comes from the famous Lewis Chessman set found on the Isle of Lewis, Scotland in 1831. According to the National Museum of Scotland, which holds 11 of the 93 individual pieces, the warder, or rook in modern-day chess, belongs to a collection that is one of the most well-known archaeological finds in the country.

A member of the family selling it said their grandfather was an antique dealer based in Edinburgh who purchased it from another dealer in the 1960s. At the time, he cataloged it simply has an “Antique Walrus Tusk Warrior Chessman,” not knowing that he had purchased such a historical and precious artifact.

“It was stored away in his home and then when my grandfather died my mother inherited the chess piece. My mother was very fond of the Chessman as she admired its intricacy and quirkiness,” said the family spokesperson in a statement. “She believed that it was special and thought perhaps it could even have had some magical significance. For many years it resided in a drawer in her home where it had been carefully wrapped in a small bag. From time to time, she would remove the chess piece from the drawer in order to appreciate its uniqueness.”

Exactly how and where the pieces were discovered remains a mystery, but history is sure to invent a few stories along the way. The set was apparently unearthed in April 1831 in the sands of an inlet on the northwestern part of the Island. Another telling of the story speaks of a grazing cow who accidentally revealed the chessman – of course, other tales of murdering sailors swimming ashore with their booty paint the history books. David Laing, a fellow of the Society of Antiquaries of Scotland, said two years after the discovery that “it is evident, that to serve some purpose, contradictory statements were circulated by the persons who discovered or afterward obtained possession of these Chessmen, regarding the place where the discovery was actually made."

Over the years, the chess pieces were eventually split between antiquities dealers throughout the country with many of them winding up in the British Museum and National Museum of Scotland. It’s believed that the set came from Norway and was carved in in the 12th or 13th centuries and belonged to a trader who might have buried the set after a shipwreck. The good condition of the pieces and general lack of wear suggests that they never reached their destination.