A large, diamond ring is expected to fetch £350,000 ($650,000) at an auction 30 years after its owner paid £10 ($18) for it at a car boot sale, thinking it was a costume jewel.
The “exceptionally-sized” stone was presumed not to be real because 19th Century diamonds were not cut to show off their brilliance like today’s gems.
And so the owner, unaware of its value, wore it for decades.
The 26.27 carat, cushion-shaped, white diamond is going under the hammer at Sotheby’s in July.
The auction house’s head of London jewellery department Jessica Wyndham said that after around 30 years wearing the ring, the owners bought it into Sotheby’s after a jeweller told them it could have substantial value.
“They came in with the idea that it might be real and they had no idea of its value,” she said.
The diamond is thought to have been cut in the 19th Century but its history and how it arrived at the car boot sale, is unknown.