Why produce two Mona Lisas, one a deluxe version entirely from the master’s brush, and one not? Since a scholar at the University of Heidelberg found a manuscript note from 1503, mentioning a Leonardo painting of “the countenance of Lisa del Giocondo,” the sitter has been known for certain.

Previously, the question of her identity was confused by a description of Leonardo showing the picture to a visitor in 1517, and -- apparently -- describing it as “a certain Florentine lady done at the instigation of the late Magnifico Giuliano de’ Medici.”

This was puzzling because Lisa del Giocondo, nee Gherardini, was married to a Florentine merchant named Francesco del Giocondo. So why would Giuliano de Medici (1479-1516), third son of Lorenzo the Magnificent, want a picture of her?

What if, as Charles Nicholl suggested in his biography of Leonardo, the lady had two admirers: her husband and a wealthy, exiled aristocrat? Giuliano and Lisa were both born in 1479, and belonged to the same elite Florentine circles. And what if the picture now in Madrid was in Florence during the 16th century, and seen by Vasari? That’s all speculation, of course, yet with Leonardo it’s always hard to resist.