A Swiss foundation says that another version of Leonardo da Vinci's masterpiece 'Mona Lisa' has undergone new tests and verified to be an original by the Renaissance painter, not a later copy.

The non-profit Mona Lisa Foundation announced Wednesday that new tests show that the Swiss version was painted between 1501 and 1505, well before the Louvre's famous 'Mona Lisa' of 1516.

Carbon dating tests revealed the canvas was even earlier, from between 1410 and 1455. The Louvre's portrait is on wood, not canvas.

The Zurich-based institute also claims that "sacred geometry" used by Leonardo is evident and documented by the specialist Alfonso Rubino.

Many art experts have decried the Swiss 'Mona Lisa' as a copy which lacks the finesse of the Louvre's original.

Known as “The Isleworth Mona Lisa” for the London suburb where a previous owner lived, the painting is said to depict Lisa del Giocondo, circa 1505, as a younger woman, twenty years earlier than "Mona Lisa."

An international consortium owns the picture now and a “Mona Lisa Foundation” was formed to verify decades of research over its authenticity.