Isleworth Mona Lisa
According to Leonardo's early biographer Giorgio Vasari, Leonardo had started to paint "Mona Lisa" in 1503, but "left it unfinished". However, a fully finished painting of a "certain Florentine lady" surfaced again in 1517, shortly before Leonardo's death and in his private possession. The latter painting almost certainly is the one that now hangs in the Louvre. Based on this contradiction, supporters of the authenticity of the "Isleworth Mona Lisa" claim it is the unfinished "Mona Lisa", made at least partially by Leonardo, and the Louvre "Mona Lisa" a later version of it, made by Leonardo for his own use.
Lisa del Giocondo
Speculation assigned Lisa's name to at least four different paintings and her identity to at least ten different people. By the end of the 20th century, the painting was a global icon that had been used in more than 300 other paintings and in 2,000 advertisements, appearing at an average of one new advertisement each week. In 2005, an expert at the University Library of Heidelberg discovered a margin note in the library's collection that established with certainty the traditional view that the sitter was Lisa. The note, written by Agostino Vespucci in 1503, states that Leonardo was working on a portrait of Lisa del Giocondo. The "Mona Lisa" has been in custody of France since the 16th century, when it was acquired by King Francis I; after the French Revolution, however, it came into the possession of the people. Today about six million people visit the painting each year at the Louvre in Paris, where it is part of a French national collection.