Tiny imperfections in an old painting found in a closet of a small West Newbury, Mass. church are hardly noticeable to an amateur's eye.

But to the studied gaze of John K. G. Shearman, a Harvard art historian, they are tantamount to reasonable doubt that the painting is entirely the work of an old master.

Shearman, who is Adams University Professor, disputes the claim by art experts and auction house officials that the painting, Madonna and Child, is entirely the work of Andrea del Sarto, a Renassiance master in Florence.

Madonna and Child is definitely a product of del Sarto's studio, Shearman admits--but much of the colorful painting was likely composed by one of del Sarto's assistants, he said.

The work hung in the choir stall of the All Saints Episcopal Church in West Newbury until about 20 years ago. It then found its way into a coat closet. Though church elders knew of the painting, they did not know of its value. So it collected dust.

Last year, in need of money to renovate, the church called two high-end New York auction houses, Sotheby's and Christie's, to evaluate the painting.

Anthony Crichton-Stuart, who directs the "old master" paintings department at Christie's, traveled to West Newbury to investigate.

"I thought this was a most interesting painting, probably from del Sarto's studio but with condition problems," Crichton-Stuart told the New York Times.

In his final appraisal, Crichton-Stuart valued the painting at $100,000.

Christopher T. Apostle, an expert on old master paintings at Sotheby's, said he disagreed. "While all the old documents said it was a copy, when I saw the painting I realized it was high quality and from the 16th century," he told the Times.

He also said the curators from the Metropolitan Museum of Art in New York, the National Gallery in London and an independent Italian scholar were all convinced it was an original from del Sarto. On NBC's "Today" show, Mr. Apostle restated his opinion. "It's in very good condition," he said.

Shearman, who is well-connected in art circles, wrote a letter to Sotheby's in early December, saying he doubted the painting was wholly authentic.

"Without question, it comes out of his workshop," Shearman said in an interview.

He said the painting's outer layers were likely painted by one of del Sarto's assistants, while the master etched the figures beneath.

As soon as he reached his conclusion, "I told them about my findings as soon as I saw the painting in early December," he said.

Though a prominent art historian was on the record with his doubts about the painting, Sotheby's did not print his criticism in the auction's catalogue.

Shearman said that the auction house ignored his concerns.

Sotheby's counters that the omission to communication problems--that Shearman did not return their phone calls seeking his permission to print his letter.

Shearman, however, said he does not remember receiving any phone call from Sotheby's. "They did not get back to me," he said.

"It is not uncommon to have disagreements on the authentity of old masters," Shearman said. "[But] their handling was very unusual," he said.

Southeby's was closed for the holiday and unavailable for comment.