Brown Morton opens a book about Winslow Homer to a photograph of a painting very similar to the one hanging above him to the left. He has been trying to prove its authenticity for decades. (Katherine Frey/The Washington Post)

Brown Morton was flipping through a stack of framed artwork at Thieves Market Antiques & Estates in Northern Virginia when he noticed dust covering the bottom right corner of one piece: an oil painting of the sea crashing onto cliffs. It was early 1961, and Morton, then a senior at the University of Virginia, licked his thumb and ran it across the dusty spot to see the signature. Instantly, he grew giddy over the five capitalized ­orange-ish letters that came into view: HOMER.

The discovery set Morton on a decades-long quest to prove that the seascape he scooped up for $20 that day was a genuine Winslow Homer, the American master whose paintings have sold for seven-figure prices. (Microsoft founder Bill Gates reportedly paid $30 million in 1998 for the last Homer still in private hands.)

But getting Morton’s alleged Homer verified has been far more difficult than he ever imagined. Despite thrilling stories of a Van Gogh worth a fortune discovered in an attic or a $2 million Andy Warhol sketch purchased for $5 at a garage sale, most people who suspect that they’ve found a masterpiece are unable to win over the experts.

What makes Morton so distinct in the class of “Antiques Roadshow” obsessives is that he comes from a profession dedicated to artistic and historic stewardship. He spent his entire career traveling the world as an architectural conservator for the Interior Department and various international organizations, helping preserve temples from Vietnam to Indonesia and other historic buildings in Italy and Jordan.

He’s 77 now, retired and living in Leesburg, Va., where the 24-by-29-inch object of his art hopes hangs in his home office above his Apple computer. He hasn’t given up on demonstrating the painting’s provenance.

Brown Morton believes he purchased an original Winslow Homer painting for $20 at an auction in 1961. It is hanging in his home office in Leesburg, Va. (Katherine Frey/The Washington Post)

“I am still chasing it,” Morton acknowledged. “Is it definitely a yes? Or definitely a no? Or will we always be in the ‘Land of Maybe’? At my age, I hope to discover the truth before a whole lot more time has elapsed, and in the time I may have left.”

‘It is not impossible’

The auctioneer started the bidding at $500 — more, in those days, than an entire year’s tuition at U-Va. No one besides Morton, then in his early 20s, appeared to have any interest in the painting. The price fell and fell. When it reached $20, Morton, the lone bidder, shot his hand toward the ceiling. The auctioneer’s hammer slammed down. And the gold-colored framed painting was all his.

But was it a real Homer?

The next day Morton and a friend drove the painting to the National Gallery of Art in Washington. They asked the guards whether they could show the piece to someone for inspection. They wound up meeting John Walker and H. Lester Cooke, then the director and curator of paintings, respectively.

Walker and Cooke, both now deceased, examined the work with an infrared and ultraviolet light to see whether the signature had been painted onto the artwork simultaneous to its original execution or had been tacked on later. Their conclusion: The painting’s signature was likely applied at the time of the artwork’s conception.

“One of them, I can’t remember which, said to me, and I’ll never forget this, ‘It is not impossible that this is a genuine work of Winslow Homer,’ ” Morton recalled. “I have lived for more than 50 years on those words.”

Brown Morton found this painting glued face down to the back of the seascape he believes is an Winslow Homer. The man might be John Gatchell, Homer's favorite model. (Katherine Frey/The Washington Post)

The men recommended that he send an image of the painting to Lloyd Goodrich, a leading Homer expert and the director of the Whitney Museum of American Art in New York. So Morton had the painting photographed and sent to Goodrich.

In March 1961, Goodrich got back to Morton. “I am very sorry to say that on the basis of the photograph, I do not feel that there is much chance of this picture being a genuine work by Winslow Homer,” wrote Goodrich, who at the time was organizing Homer’s catalogue raisonné, the compendium of all of the painter’s verified works.

Goodrich explained that the auction house painting contained a style, brushwork and drawing not in keeping with Homer. Worst of all, the signature — the very thing that sparked Morton’s interest at the auction house — “looks dubious,” Goodrich wrote.

“As you probably know, there are many works falsely attributed to Homer and I am afraid that this is one of them,” wrote Goodrich, who died in 1987.

Morton, though, was undeterred. He believed his painting — with a gray sky over white water crashing onto brown cliffs — was similar to a Homer titled “High Cliff, Coast of Maine” that hangs in the Smithsonian American Art Museum. Morton surmised his piece was Homer’s preliminary version of the more famous work, painted in 1894, that just never made it into the catalogue raisonné.

‘A pretty amazing moment’

He set aside his investigation while he pursued his career, working in Europe as an architect, marrying a Brit, then landing a job at the National Park Service in the office of archeology and historic preservation.

In the 1970s and 1980s, Morton worked on behalf of UNESCO, visiting the imperial city of Hue in Vietnam to restore temples destroyed during the Tet Offensive. Then, he was off to help restore Borobudur, a stepped pyramid and the largest Buddhist monument in the world, a trip he chronicled for National Geographic magazine.

“My keen interest is to search for the spiritual secrets of other times and other places,” Morton wrote of his journey in a 17-page spread in the January 1983 issue.

A few years later, he took his seascape to conservation master’s students at a program run by the University of Delaware and the nearby Winterthur Museum, Garden & Library. There, the students studied the piece’s pigments and found that someone had “overpainted” the piece’s sky with materials used only in the 1920s, well after Homer had died in 1910, according to the examination report.

Richard Wolbers, a professor of art conservation at the University of Delaware who helped examine Morton’s painting, said the finding was not that alarming. “I thought the painting looked to me like a sketch begun by an artist but not yet finished, and then someone else finished it off for him,” he said.

The museum’s report kept Morton’s hope alive: “It is difficult to attribute the painting to Homer . . . yet there is no firm evidence against such an attribution.”

But the verdict kept see-sawing. In 1987, John Holverson, then the director of the Portland Museum of Art, the Maine home to the Winslow Homer Studio, where the painter lived and did much of his work, examined a photograph of the painting. Holverson ruled out attributing it to Homer, according to his letter that Morton keeps on file.

Then, more than a decade ago, came what Morton regards as a breakthrough at Winterthur: Wolbers peeled off the back linen covering, while Morton watched. The men were startled: They found a second painting. The piece pictured an elderly white-bearded man wearing what appeared to be a sailor’s cap with a gold-colored pin on the front. Could it be John Gatchell, Homer’s often-used model? The man looked just like Gatchell.

“I thought it was a pretty amazing moment for Brown,” Wolbers said. “This could be the smoking gun.”

Jennifer Mass, a senior scientist at Winterthur, told The Washington Post he could bring his painting back for further study. New technologies could be used to more closely inspect the pigments and their interactions with the environment to see whether they’re consistent with something painted in Homer’s time.

Even so, Mark Bessire, the Portland Museum of Art’s current director, said it’s very difficult for experts to authenticate without a piece’s detailed history and provenance. “Because of the visibility and value of these paintings, it’s becoming riskier and riskier to authenticate works of art,” Bessire said. “The risk to your reputation is so huge if you’re wrong, and now you can find yourself in litigation.”

In September, Morton’s youngest son, Robert Morton, 44, of Alexandria, reached out to The Post on his father’s behalf. Could the newspaper help solve the case? “He’d be disappointed if it wasn’t real,” the younger Morton said, “but also because the hunt would be over.”

At The Post’s request, one Homer expert who insisted on anonymity examined a photo of Morton’s painting and offered an assessment: The $20 Homer is a forgery.

The expert made the ruling based on existing records of known Homer forgeries, including an archived photograph of a forged Homer painting identical to the piece Morton purchased in 1961.

Morton, however, wasn’t buying it. “Then why,” he asked, “was John Gatchell glued facedown on the back of my picture? No one forging this picture would have painted an additional forgery and glued it to the back of the forgery.”

Morton is still waiting for more evidence. “Until then,” he said, “I’ll hang my $20 Homer on the wall.”