Sunset at Montmajour, a Van Gogh painting that languished in the attic of a Norwegian collector for years, has been authenticated by the Van Gogh Museum in Amsterdam.
The piece is a relatively large-scale painting and dates from 1888, a period Van Gogh spent in Arles in the south of France. Many consider his work from this time the high point of his artistic achievement.
The work had been dismissed as a forgery by the museum in 1991 - partly because the artist had not signed it. However, new forensic research techniques, including analysis of the paint pigments used, have revealed that the work is genuine. Letters were also found that made reference to the painting, including one from Van Gogh to his brother Theo that described it and identified the date on which it was painted.
Louis van Tilborgh and Teio Meedendorp, two senior researchers of the Van Gogh Museum, commented: "We carried out art historical research into the style, the depiction, use of materials and context, and everything we found indicated that this is a work by Van Gogh.
"Stylistically and technically speaking, there are plenty of parallels with other paintings by Van Gogh from the summer of 1888".
Van Gogh is one of the world's best-known and most popular artists. The record price paid for a Van Gogh remains the $82.5m achieved for The Portrait of Dr Gachet at Christie's in 1990. When adjusted for inflation it is the highest price paid for any artwork at auction.
Tilborgh and Meedendorp added: "The tension between dream and reality is what makes this painting all the more attractive. We see Van Gogh visibly working, struggling almost, and this adds to the charm of this work.
"It belongs to a special group of experimental works that Van Gogh at times esteemed of lesser value than we tend to do nowadays."
The painting will be on display in the Van Gogh Museum in Amsterdam from September 24.