A charcoal drawing known as the "nude Mona Lisa," long attributed to one of Leonardo da Vinci's students, may have been drawn by the master himself, according to experts at the Louvre in Paris.

It's hard to miss the resemblance between the woman in da Vinci's famous 16th-century painting and the semi-nude subject of the "Monna Vanna," a colorless sketch that has been held in the collection of the Condé Museum, north of Paris, since 1862. The familiar half-smile lingers above that pointed chin, while her hands are folded in exactly the same way.

Other similarities have caught the attention of researchers looking into the work's origins ahead of a planned 2019 exhibition at the Condé that will mark