This painting by Leonardo is valuable to art historians because the artist left a visible finger print on the canvas, which lets us know that he was one of the first artists to manipulate paint with his hands to get his desired blurring effect on the canvas. This is a technique associated with modern art, making Leonardo hundreds and hundreds of years ahead of his time.
Leonardo da Vinci
Ginevra de Benci, c. 1474/78
I am always amazed by da Vinci facts.