An earlier version of the "Mona Lisa"?

GENEVA -- The mystery behind the most enigmatic smile in art, Leonardo da Vinci's "Mona Lisa," just got more complicated.

At a coming-out party of sorts, the nonprofit Mona Lisa Foundation presented Thursday what it claims is a predecessor of the world's most famous portrait.

The "Isleworth Mona Lisa" is of a dark-haired young woman with arms crossed against a distant backdrop. The foundation insists it's no copy but an earlier version of the masterpiece.

The foundation acknowledged the painting remains unfinished, and da Vinci didn't paint all parts of the work.

Experts say the unveiling was designed to draw more attention and scrutiny about whether it's authentic: A start, more than a finish. -- AP