To the untrained eye, it was a nice enough painting. Small and wooden, old and religious; it would probably look good in the kitchen, maybe the hallway.

And that’s where it hung for years, in the home of a French woman in her 90s who reportedly assumed it was an icon of little importance and less value. She may have even considered tossing it as she prepared to move out of her house in Compiegne, north of Paris.

Had she done that, the art world would have lost a masterpiece, and she would have lost millions.

A dusty icon it was not.

The painting is titled “Christ Mocked,” and it has been attributed to the 13th-century Italian artist Cenni di Pepo, known as Cimabue, a figure widely seen as a Renaissance forefather. Experts have identified only 10 or so other Cimabue paintings, and his work remains exceedingly rare — making this improbable rediscovery even more remarkable.

“This is a hugely, hugely important discovery,” said Xavier F. Salomon, the chief curator at the Frick Collection in Manhattan, home to the only Cimabue painting outside Europe. “He’s seen as the grandfather of Western painting, and he’s very, very rare. So the discovery of a new work by him is a really incredible thing.”

The piece could fetch nearly $7 million when it’s put up for sale Oct. 27.

Its owner, the French woman who hasn’t been publicly identified, asked an auctioneer to look through her house before she moved out this summer, The Associated Press reported. The auctioneer spotted it and suggested she take it to art experts at the Turquin gallery in Paris, who concluded with “certitude” it was a Cimabue.

“You rarely see something of such quality,” Philomène Wolf, the auctioneer who discovered the painting, told Le Parisien. “I immediately thought it was a work of Italian primitivism. But I didn’t imagine it was a Cimabue.”

The 8-by-10-inch painting is in very good condition, said Salomon, whose colleague at the Frick saw the work in person last week. That’s a miracle given not only its age — nearly 800 years old — but also where it apparently hung in the Compiegne home: right above a hot plate, though it’s unclear that’s where the family did its cooking.

“If you think about it, this thing has been around for several hundred years; it’s probably been through a lot,” Salomon said. “It’s been through the French Revolution. It’s been through several wars. Works of art are more resistant than people think.”

“Still,” he added, “I wouldn’t recommend anyone putting something that old over a hot plate.”

Scholars think of Cimabue as the link between two periods of art, the Medieval and the Renaissance, Salomon said. He began adding character and dimension to Byzantine art, making it more human. He also taught Giotto, considered one of the greatest artists of the era.

“He was very on the cusp of that,” Salomon said of Cimabue. “He is the one where this shift really begins.”

The painting is part of a larger work, a companion piece to one in the Frick Collection, known as “The Flagellation of Christ” and acquired in 1950, and one in London’s National Gallery, titled “The Virgin and Child With Two Angels” and acquired in 2000. The series — which could number either four or eight, Salomon said — depicts Christ’s passion and crucifixion.

The Paris specialists matched the wood of the newly found painting to the wood of its partners, CNN reported. Then they used an infrared light to match the brushstrokes.

Writing in the Guardian, however, art critic Jonathan Jones urged the public to be skeptical of early, high-profile identifications of long-lost masterpieces.

“This is the new norm at the profitable end of the Old Masters market,” Jones wrote. “Great stories about unlikely discoveries sweep all before them, but art experts have recently been fooled by proven fakes. ... Not that I am saying this is a fake — just that the identification of old paintings is and always has been fraught with peril. It shouldn’t be accepted solely on the seller’s say-so, or because it makes a good story.”

For Salomon and others in the art world, the assembly of Cimabue’s series has been a thrilling piece-by-piece treasure hunt.

“We were all hoping that more fragments would come up,” he said. “It adds pieces to the puzzle. It allows us to understand the painter in a better way.”

At this point, the Frick Collection isn’t looking to buy the painting — “We shouldn’t be greedy,” Salomon said — but the museum would be interested in reuniting the three in an exhibit some day.

Or perhaps, in another few years, another long unrecognized Cimabue will resurface in an unlikely locale, and the picture will finally be complete.

“That happens more often than people think,” Salomon said. “Many of the great discoveries made in the last 50 years were all made in places people didn’t expect them to be.”

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