ROME - Forget her smile. An Italian researcher says the key to solving the enigmas of "Mona Lisa"' lies in her eyes. Silvano Vinceti claims he has found the letter "S" in the woman's left eye, the letter "L" in her right eye, and the number "72" under the arched bridge in the backdrop of Leonardo da Vinci's famous painting. According to the researcher, the symbols open up new leads to identifying the model, dating the painting, and attesting to Leonardo's interest in religion and mysticism. This is just the latest theory about a painting that has never ceased to intrigue scholars, art lovers and casual viewers alike. Others have claimed the painting is really the portrait of a man, or a self-portrait, while speculation over the reason for the model's famously enigmatic smile have ranged from pregnancy to mourning.