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
In 1913 English connoisseur Hugh Blaker spotted and acquired the painting which had been hanging for over a century in a manor house in Somerset, having been bought in Italy as an original Leonardo. In a monograph published shortly thereafter, Blaker's stepfather, John R Eyre, proposed that two versions of the Mona Lisa had been worked on by Leonardo; the "Isleworth" picture (named after the location of Blaker's studio in Isleworth, west London) being the first.