A painting of a nude man donated to an Oxfam thrift store in the U.K. sold for nearly $25,000 earlier this month after it was determined to be by the hand of English Impressionist painter Henry Scott Tuke.

Greg Bateman, senior valuer at Batemans Auctioneers & Valuers in the town of Stamford, said in a statement he was “stunned” to see the painting emerge from a shopping bag when it arrived at auction house. The painting had been brought in with several others by a thrift store volunteer after it was left behind by an unnamed donor.

The unsigned oil painting, Nude Study Of A Young Man (ca. 1915), measures roughly 15 by 12 inches and depicts a young man crouching and looking off to the left. The model is likely Charlie Mitchell, a boat handler.

Henry Scott Tuke, born in 1858, was a prolific painter best known for depicting nude boys and men. His works, though never explicitly sexual, have been owned by collectors including Elton John and Freddie Mercury, and have been the subject of many academic papers on gay and homoerotic work.

The newly discovered painting opened with a bid of £520 ($651) at Batemans before rapidly increasing as eight different bidders, including one phone bidder, fired off 88 bids in just six minutes.

It ultimately sold with a price of £24,800 ($31,036), after buyer’s premium, to a British collector who “will be trying to pin down a firm attribution” for the work.

“The difficulty was that it wasn’t signed and [had] no real official provenance,” Bateman told The Telegraph. “We weren’t able to speak to the person who donated it, we don’t even know a name, so we don’t know how they came by it.”

In his statement, Bateman said the collector is “extremely pleased” to have fought off stiff competition for the painting, which is the most expensive ever sold by the small auction house. The proceeds of the sale are expected to go to the charity.

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