The work, Chopping Logs Outside A Snow Covered Cabin, was found buried under junk in Glasgow’s Barras market 30 years ago.
But the piece, by Cornelius Krieghoff, was expected to fetch 100,000 times its original price when it goes under the hammer later this month.
The painting’s owner, who wants to remain anonymous, had no idea of its worth. He bought it for “10 bob” – because he liked it.
He said: “I often browse through the Barras and bought the painting because it was a great picture.
“I am surprised and delighted that my find has turned out to be such a worthwhile investment.”
The retired owner, who now lives abroad, added the Krieghoff to his collection of favourite paintings and thought nothing more about it until he began researching different artists and realised it was an original.
He took it to experts who valued it between Â£30,000 and Â£50,000.
Amsterdam-born Krieghoff, who died in 1872 at the age of 56, made his name painting Canadian landscapes and life outdoors, particularly in winter