The Mona Lisa Foundation in Zurich said scientific tests and historical records supported its claim the so-called Isleworth Mona Lisa was indeed a portrait of the same woman Leonardo immortalized in his later masterpiece.
"When we add these new findings to the wealth of scientific and physical studies we already had, I believe anyone will find the evidence of a Leonardo attribution overwhelming," foundation vice-president David Feldman said this week in a written statement.
The Mona Lisa Foundation conducted carbon dating on the canvas of the Isleworth image and determined it had been painted between 1410-1455. The Mona Lisa was created in the early 1500s.
But some art experts still have their doubts, swissinfo.ch said Saturday. One historian said artists were not yet painting on canvas in the early 1400s.