A painting that was the subject of a book by John Brewer about a 20th Century dispute over a work claimed as a Leonardo is for sale at Sotheby’s as work by an unknown artist. The New York Times reveals that the picture has undergone some scientific investigations that suggest, though it is not a Leonardo, that it may have been painted earlier than thought. The original controversy involved a family named Hahn:

Last year the Hahns’ daughter, Jacqueline, curious about the painting that has been so much a part of her family history, took it to the J. Paul Getty Museum in Los Angeles so conservators and experts could examine it.

Scott J. Schaefer, curator of paintings at the Getty, said the painting he had read so much about — a three-quarters profile of a woman thought to be Lucrezia Crivelli, a mistress of Ludovico Sforza, the duke of Milan — was not what he expected when it was unwrapped. “It was so much better than we thought,” Mr. Schaefer recalled. “This wasn’t just some copy of a painting but a skillful interpretation.”

Yet scientific analysis did not provide the answers he had anticipated. “When I looked at it, I thought it dated from about 1820 to 1830,” he said. Many experts thought it could have been the work of a French neo-Classical painter like Ingres. “But science disappointed us,” Mr. Schaefer said.

For starters, while the Louvre painting is on panel, this painting was on canvas. Poplar panel was a typical material for late 14th-century Florentine portraits like this one was thought to have been, while canvas was a material that became more common later. Studies also showed that the canvas was primed with a double red pigment that was typical of French paintings from the late 17th century to the late 19th century. Pigment analysis also revealed the use of lead-tin yellow, a color employed in the 17th century that reappeared again only in paintings dating from the mid-20th century.

These findings suggest that the “Portrait of a Woman Called ‘La Belle Ferronnière’ ” was probably painted before 1750. “After that it would have been hard to believe that lead-tin yellow would have been used because the formula for it was lost,” Mr. Wachter said.