An Italian pensioner who unknowingly bought a stolen Gauguin for a pittance has been allowed to keep it after it was valued at $50 million.

The man, who has requested anonymity out of fear the painting could attract thieves, acquired the work along with another piece at an art sale in Turin in 1975.

The auctioneers told him they were worthless "rubbish," but they were in fact an 1889 Gauguin entitled "Fruits on a Table" or "Still Life with a Small Dog," and a work by Pierre Bonnard entitled "Woman with Two Armchairs," now thought to be worth $850,000.