The saw from a giant sawfish shark was sold at a recent Dee Atkinson & Harrison sale in Driffield.
The curiosity, valued at £300-£400, was sold by a Hull pensioner who was a member of the team on board a United Nations research vessel when the huge fish – which can grow up to 25ft in length – was captured during a scientific expedition in the Indian Ocean in 1969.
Saleroom manager Pippa Whiteley said it was the largest example she had seen.
She said: “There was a little bit of interest before the sale but that didn’t materialise into a huge amount of bidding.
“It’s a specialised object for a specialised buyer – not everybody has room for one and not everybody likes the idea of it.”
All seven species of sawfish are now on the International Union for Conservation of Nature’s Red List of endangered species, with some experts maintaining that they are the most threatened family of fishes in the world today.
The sale required a Convention for International Trade in Endangered Species licence.
Had it been caught after 1975 it would not have been legally possible to sell the saw.