A Swiss-based art foundation says tests on the Isleworth Mona Lisa support claims that it’s an earlier version of Leonardo da Vinci’s portrait hanging in the Louvre in Paris.

Fabrice Coffrini / AFP / Getty Images A side-by-side comparison of the Isleworth Mona Lisa (L) and the Louvre’s Mona Lisa in Geneva on Sept. 27, 2012.

New tests appear to have confirmed thatthe Isleworth Mona Lisa — a painting thought to be an earlier version of Leonardo da Vinci’s famous portrait — is indeed authentic, reportsthe Guardian.

The tests, including one by a specialist in “sacred geometry” – the geometry used in the planning and constructing of religious structures – and one by the Swiss Federal Institute of Technology in Zurich, were carried out after the Geneva unveiling of last September.

(MORE: Mona Lisa: Was There More Than One?)

According to a carbon-dating test by the Zurich Institute, the canvas of the Isleworth painting dates to somewhere between 1410 and 1455, refuting claims that it was a late 16th century copy, the Huffington Post reported. , which appears to depict a younger version of the same woman in the Mona Lisa hanging in the Louvre in Paris,

Italian geometrist Alfonso Rubino, who has made extended studies of Da Vinci’s Vitruvian Man, determined that the 15th century Isleworth portrait – named after the London suburb where it was kept by British art connoisseur Hugh Blaker early in the last century – conformed to Da Vinci’s basic line structures, the Guardian said.

According to the Independent, David Feldman, vice-president of the Mona Lisa Foundation, said, “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.”

The Islesworth Mona Lisa appears to depict a younger version of the same woman who appears in the Mona Lisa that hangs in the Louvre Museum in Paris. That painting, which has hung in the Louvre for more than three centuries, is believed to have been painted between 1503 and 1506. It was long thought to be the only extant version of Da Vinci’s portrait of Lisa Gherardini, also known as Lisa del Giocondo. However, brush-stroke analysis conducted by U.S. physicist John Asmus last September sprouted rumors that the Isleworth and the portrait in the Louvre were painted by the same artist, the Independent reported.

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