Along with Factory workers, Simon sought out three of Warhol’s early dealers and champions: Sam Green, Irving Blum, and Ivan Karp. All of these art-world figures agreed that Simon’s self-portrait was real. Karp was especially supportive: he, too, had had a Warhol painting denied by the board.

“I was his first art dealer, in 1961, and I was dedicated to his good cause!” the twinkly-eyed Karp, 77, declares of Warhol from the office of his venerable West Broadway gallery, called OK Harris. So Karp was stunned when a buyer to whom he’d sold a two-panel self-portrait by Warhol informed him that the then newly formed authentication board had declared it “not the work of Andy Warhol.”

Karp had bought the painting in the 1960s, knowing full well that its creation had been atypical. A Michigan art professor had contacted Warhol to say that his class wished to produce a Warhol silkscreen, and could the artist advise them? Warhol blithely obliged. When the students were done, Warhol went to visit the class, pronounced himself delighted by the two square panels, one on top of the other, each of which bore his silkscreened image - one in silver, one in blue - and signed the upper one of them. When the professor offered to sell Karp the work, the dealer snapped it up, convinced it was merely another of the artist’s experiments in method, no less legitimate than any of his other works.

To Karp, the proof was in the penmanship. “The signature was the confirming act on the part of the artist!” he declares. “That meant this is what he meant it to be!” As Karp knew, the lack of a signature on a Warhol work meant nothing: the artist produced works in such volume that he often waited until they were sold before signing them. But when Warhol did sign a work, and the signature could be confirmed, how could the board ignore it? “To be uninterested in the signature is extraordinary,” Karp fumes. “That’s the whole thing for authenticators of classical paintings, after all. In my 46 years in the business, I’ve never come across anything like this.”

Karp had no choice but to take the painting back and refund the buyer his $40,000. After stewing for a while, he decided to submit the painting himself. “I figured when I submitted it under my name, from my loyalty to Warhol’s career . . . That they would honor that,” Karp says. It came back with the DENIED stamp on the back of the canvas. Furious, Karp discarded that one and hung the unspoiled panel in his office.

“There it is,” Karp says, gesturing to the wall behind him. As salable work, Karp figures, the small panel would be worth about $90,000. Now it’s just a decorative wall hanging. “And you know what?” Karp says, fuming again at the memory. “I found a paper in my files, from Vincent Fremont, confirming the picture.”

Behind a big wooden desk in his loft-like Manhattan office at One Union Square, framed by rows of art books behind him, Vincent Fremont at 53 has the rumpled, shambling look of a college art professor, and a casual, self-deprecating charm to match. Yet he holds a post of high power in the art world, one that makes a lot of art dealers nervous. As exclusive agent for the Warhol foundation, which was formed in 1987, Fremont decides which galleries and museums will get Warhol shows, and which dealers will get works to sell. From all paintings, drawings, and sculpture that the foundation sells, he gets a commission: originally 10 percent, now 6 percent. Since its inception, the foundation has sold about $150 million worth of Warhol’s art. Fremont, who showed up as a worshipful teenager at the Factory in 1969 to sweep the floors, is now a multimillionaire.

Fremont readily admits that in the tumultuous period after Warhol’s death he authenticated Karp’s double-panel self-portrait. In the absence of any authentication board at that time, he and Fred Hughes took on the thankless job, as he puts it, of judging works that came in for review. “You wouldn’t believe the stories that some people brought, huge packages of stories that were totally fabricated,” Fremont recalls. “It’s much more complicated than you’d think.” In the case of the Karp self portrait, he remembers the circumstances: the Michigan art class, Warhol’s visit. How then could the board later reverse his judgment? “The present board is its own body,” Fremont says evenly. Did the board decide that work done off-site was invalid, despite Warhol’s approval of it? That impression, he says without elaboration, is “understandable but not correct.”

Hughes did most of the authenticating until his eyesight began to fail from multiple sclerosis. As Hughes’s condition worsened, Fremont became the estate’s chief authenticator. (After a protracted and painful decline, Hughes dies in 2001.) Dealers began muttering that this created, at the least, an apparent conflict of interest - one that might lead Fremont to reject works presented by outsiders in order to promote sales of the foundation’s own stock, for which he would get his sales commission. Fremont denies that. “It was never about commerce,” he says of the authenticating. “It was about the integrity of the artist’s work.”

Eight years after Warhol’s death, the authentication board was formed. It would be an expert panel wholly separate from, but underwritten by, the Warhol foundation, which would continue to sell Warhol’s art. One member was David Whitney, a Warhol acquaintance who had once hung a show of Warhol drawings at New York’s Whitney Museum of American Art. (No relation to the museum’s founding family, he was, and is architect Philip Johnson’s companion.) Another, Neil Printz, was a well-regarded academic, while Georg Frei worked at the Thomas Ammann Fine Art gallery in Switzerland. Interior designer Jed Johnson, a close friend of Warhol’s for many years, was a fourth member, though he would serve for little more than a year - a victim of the crash of TWA Flight 800. There was briefly one other member of the board: Vincent Fremont.