Art experts say a drawing that appears to be the Mona Lisa, but naked, was probably drawn by Leonardo da Vinci himself.
The 'Mona Vanna' has for centuries been credited to his students, but a new analysis suggests the master might have played a big hand in it - his left, to be specific.
Mathieu Deldicque, curator of the Condé Museum - which has housed the 16th-century charcoal artwork since 1862 - says it was clearly drawn by a left-hander.
"It is a work of very great quality done by a great artist," he told AFP.
Previous attempts to work out who painted the topless woman were led astray by a small patch in the upper-right corner, said Mr Deldicque, which appears to have been added at a later date by a right-handed person.
But the rest is covered with "left-handed charcoal marks pretty much everywhere", and there's also evidence of a blending technique favoured by da Vinci.
"It is almost certainly a preparatory work for an oil painting," said Mr Deldicque, noting the woman is posing similarly to the subject of the 'Mona Lisa, which is indeed an oil painting - probably the most famous in the world.
Mr Deldicque admitted despite the evidence, it may never be "absolutely certain" who drew it.