The charcoal drawing was previously attributed as having come from Da Vinci’s studio, possibly drawn by one of his students, but now experts believe there is enough evidence to suggest it is at least partly by the great painter and was a pre-piece for his most famous portrait.
The sketch has been held since 1862 in the collection of Renaissance Art at the Conde Museum at the Palace of Chantilly, north of Paris.
“The drawing has a quality in the way the face and hands are rendered that is truly remarkable,” curator Mathieu Deldicque told AFP news agency.
“It is not a pale copy. We are looking at something which was worked on in parallel with the Mona Lisa at the end of Leonardo’s life.
“It is almost certainly a preparatory work for an oil painting.”
Deldicque told Le Parisiene some of the clues experts took into account are that the portraits are almost the same size and that the hands and body are virtually identical. Small holes pierced around the figure also suggest it may have been used to trace onto a canvas.
Bruno Mottin, a conservation expert at the Louvre, told the newspaper the sketch is very fragile and pointed out the hatching at the top of the picture was drawn by a right-handed artist.
Noting Da Vinci was left handed, thus making it likely more than one artist worked on it, he warned: “We have to be careful. It’s a long process.”
The Mona Lisa hangs in Paris’s Louvre museum and is probably the most famous painting in the world, depicting a young woman with her hands gently folded on her lap.
The museum says it was painted between 1503 and 1506 and is thought to be of Lisa Gherardini, the wife of a Florentine cloth merchant named Francesco del Giocondo.
Leonardo was also a talented sculptor and anatomist. As well as being known for his paintings, he conceived modern machines like helicopters and tanks many centuries before they were finally built.