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.
Isleworth Mona Lisa
The "Isleworth Mona Lisa" is wider than the "Mona Lisa" in the Louvre, having columns on either side which also appear in some other versions. The Louvre painting merely has the projecting bases of columns on either side, suggesting that the picture was originally framed by columns but was trimmed. However, experts who examined the "Mona Lisa" in 2004–2005 stated that the original painting had not been trimmed.