AMSTERDAM (AP) - A painting that sat for six decades in a Norwegian industrialist's attic after he was told it was a fake Van Gogh was pronounced the real thing Monday, making it the first full-size canvas by the tortured Dutch artist to be discovered since 1928.
Experts at the Van Gogh Museum in Amsterdam authenticated the 1888 landscape "Sunset at Montmajour" with the help of Vincent Van Gogh's letters, chemical analysis of the pigments and X-rays of the canvas.
Museum director Axel Rueger, at an unveiling ceremony, called the discovery a "once-in-a-lifetime experience."
"This is a great painting from what many see as the high point of his artistic achievement, his period in Arles, in southern France," Rueger said. "In the same period, he painted works such as "Sunflowers,' "The Yellow House' and "The Bedroom.'"
Museum officials would not identify the owner who brought the artwork to them in 2011 to be authenticated. Van Gogh paintings are among the most valuable in the world, fetching tens of millions of dollars on the rare occasions one is sold at auction.
The artwork will be on display at the museum beginning Sept. 24.
The roughly 37-by-29-inch "Sunset at Montmajour" depicts a dry landscape of twisting oak trees, bushes and sky, and was done during the period when Van Gogh was increasingly adopting the thick "impasto" brush strokes that became typical of his work in the final years of his short life.
It can be dated to the exact day it was painted because he described it in a letter to his brother, Theo, and said he had painted it the previous day - July 4, 1888.
"At sunset I was on a stony heath where very small, twisted oaks grow, in the background a ruin on the hill and wheat fields in the valley," Van Gogh wrote. "It was romantic. ... The sun was pouring its very yellow rays over the bushes and the ground, absolutely a shower of gold."
But then Van Gogh confessed that the painting was "well below what I'd wished to do." Later he sent it to Theo to keep.
Van Gogh struggled with bouts of mental distress throughout his life and died of a self-inflicted gunshot wound in 1890. He sold only one painting during his lifetime.
According to a reconstruction published in The Burlington Magazine by three researchers, the painting was recorded as number 180 in Theo's collection and given the title "Sun Setting at Arles." It was sold to French art dealer Maurice Fabre in 1901.
Fabre never recorded selling the work, and the painting disappeared from history until it reappeared in 1970 in the estate of Norwegian industrialist Christian Nicolai Mustad.
The Mustad family said Mustad purchased it in 1908 as a young man in one of his first forays into art collecting, but was soon told by the French ambassador to Sweden that it was a fake. Embarrassed, Mustad banished it to the attic.
After Mustad's death in 1970, the distinguished art dealer Daniel Wildenstein said he thought the painting was a fake Van Gogh or possibly the work of a lesser-known German painter, and it was sold to a collector. The museum would not say who bought it or whether it had been resold since then.