Antiques dealer acquired piece in 1964 and family mostly kept it out of the way in a drawer

A newly discovered Lewis chessmen piece that was bought for £5 in 1964 has sold at auction for £735,000.

The small walrus tusk warrior figure was revealed last month to be a missing piece from a set considered one of the most stupendous wonders of the medieval world.

At a Sotheby’s auction in London on Tuesday, bidding for the piece opened at £480,000 and quickly rose to the low estimate figure of £600,000 but went no further, falling short of the upper estimate of £1m. With commission, the amount paid by the anonymous buyer was £735,000.

Alexander Kader, a Sotheby’s expert who spent a year studying the chess piece, said: “This is one of the most exciting and personal rediscoveries to have been made during my career. It has been such a privilege to bring this piece of history to auction and it has been amazing having him on view at Sotheby’s over the last week – he has been a huge hit. When you hold this characterful warder in your hand or see him in the room, he has real presence.”

The Sotheby’s sale also featured 6th-century Byzantine jewellery, 15th-century German stained glass and 16th-century Spanish polychromed wood sculptures. But the star was the 8.8cm-tall Lewis chessman, displayed in a transparent case in front of the auctioneer Harry Dalmeny and three Sotheby’s clerks.

It was identified as a missing piece from a hoard that was discovered in the sandbanks of Lewis, in the Outer Hebrides, in 1831. The chessmen are well known in popular culture thanks to the children’s television series Noggin the Nog and Ron Weasley’s perilous chess game in Harry Potter and the Philosopher’s Stone.

A total of 82 Lewis chessmen pieces are in the British Museum in London and 11 are in the National Museum of Scotland in Edinburgh. Five are missing.

The newly discovered piece was bought by an antiques dealer for £5 in 1964 and passed down through his family, who mostly it kept out of the way in a drawer. The family were unaware of its significance until the piece was taken to Sotheby’s for assessment.

The chessmen were most likely made in Trondheim, Norway, of which the Western Isles were part, between 1150 and 1200. Theories of how they ended up in Lewis range from the hoard being part of a shipwreck to them being hidden for safekeeping by a travelling merchant.

A former British Museum director, Neil MacGregor, included them in his A History of the World in 100 Objects series for BBC Radio 4 and talked of how the “much-loved pieces take us into the heart of the medieval world”. He said they showed not only high status, wealth and power but also “knowledge, taste and intellect”.