The cup was bought in China in the 1920s or 30s
An intricately carved 17th Century cup which had been in a North Lincolnshire attic for 25 years has sold for four times its estimated price at auction.
The Chinese libation cup, which is made out of a rhinoceros horn, had been valued at between £20,000 and £30,000.
But it went for £80,000 at an auction house in Brigg on Saturday.
Before the sale, auctioneer Craig Bewick said its owners were "shocked but pleased" by the cup's valuation. "It is worth a fortune," he said.
"It's a fantastic thing," Mr Bewick added.
"Libation cups were communal drinking vessels that were used on important ceremonial occasions.
"Rhinoceros horn examples of this age are extremely rare, to put it mildly."
The cup was discovered when its owners brought it to a routine valuation day at Brown and Co auctioneers in Brigg, near Scunthorpe.
It had been bought by the grandfather of the present owner in China in the 1920s or 30s. They had tried to sell it in the 1980s, but were told it was only worth a few hundred pounds.
The cup is carved with scenes from 17th Century Chinese life
"Actually the valuer was right at the time," Mr Bewick said.
"A quarter of a century ago there was not a huge amount of interest in Chinese rhinoceros horn libation cups, but things have changed rather a lot since then."
He added that a lot of interest had been shown in the cup from buyers in China, many of whom had inquired about making the trip to Brigg in person for the auction.
But Mr Bewick added that the cup was lacking something that would make it even more desirable - a maker's mark.
"Sadly the craftsman will almost certainly remain anonymous forever, simply because he did not mark his work," he said.
"That's really infuriating.
"The pre-sale estimate is £20,000-£30,000 but had there been a craftsman's mark we would almost certainly have been looking at a valuation of in excess of £100,000."