It may be the best known portrait ever produced. It was created between 1503 and 1506 by Leonardo da Vinci, crafted in oil on a wooden board. It is known as “Mona Lisa,” but for centuries art historians have expressed uncertainty over the identity of the subject. This week, however, German researchers believe the mystery has been solved. Veit Probst, the director of the Heidelberg University Library, stated in an interview with the German radio network Südwestfunk that it was now “confirmed” that the figure in the painting is the wife of a Florentine merchant, Lisa del Gioconda. The radio report is summarized in the current issue of the Hamburg newsweekly Der Spiegel.

The painting, which hangs in the Louvre, has long been labeled “La Gioconda” based on reports from the sixteenth century linking da Vinci to Lisa del Gioconda as his “favorite.”

Probst was previously the head of the Heidelberg University Library’s manuscript department. That’s where he came across an incunabulum (a primitive sort of print) which contained a marginal notation of its owner, a handwritten indication of the identity of the person portrayed. The owner of this print was also established–he was a contemporary of Leonardo’s and knew him.

The discovery was published for the first time in an exhibition catalogue at Heidelberg University. Probst has also prepared a scientific essay on the discovery which is set to be published in three weeks.

Writings on the portrait in the past have speculated that “Mona Lisa,” with her world famous smile, was an unknown mistress of da Vinci’s or that it was a coded self portrait of da Vinci himself.