Fingerprint may solve mystery

The "Adoration," a round picture with a diameter of about three feet, features precious materials such as lapis lazuli and gold leaf that give it luminosity. The gold was used not only for halos and garments, but also to give highlights to the sky and landscape.

The fingerprint on paintings was an enigmatic sign that nonetheless would identify the maker beyond doubt.

A 1926 study by art critic Roberto Longhi generated wide support for the Fra Bartolomeo thesis, but doubts have remained.

Fra Bartolomeo, originally Baccio della Porta, became a Dominican friar after falling under the influence of the fire-and-brimstone sermons of Girolamo Savonarola. He owes an artistic debt to Raphael.

Leonardo's "Lady with an Ermine" hangs in Krakow's Czartoryskich Museum. It represents a teenage beauty whom scholars believe to be Cecilia Gallerani, mistress of Milan's ruler, Lodovico Sforza, who was the artist's patron at the time.