This 15th-century portrait of a young woman may be a nuptial portrait painted by Leonardo da Vinci. (Museo Ideale Leonardo Da Vinci/Associated Press)

A small picture of a young woman in profile owned by a Canadian collector may be a work by Leonardo da Vinci.

Art experts say there is strong evidence the picture is by Leonardo after finding a fingerprint on the Renaissance-era painting that matches another fingerprint found on his St Jerome in the Vatican.

The fingerprint was found by Peter Paul Biro, a Montreal-based forensic art expert, through multispectral analysis, which detects images unseen by the naked eye, according to the Guardian newspaper.

The painting is owned by Canadian-born collector Peter Silverman, who bought it two years ago for just over $20,000.

A Christie's assessment of the painting advertised it as by an unknown 19th- century German artist, but Silverman believed it might be older and of more noble lineage.

The hairstyle and robe worn by the young woman in the ink and chalk image is consistent with Milanese fashion of the late 15th century, experts say.

Carbon dating also suggests the painting dates from the late 1400s, when Leonardo would have been painting.

Silverman consulted both Biro and Dr. Nicholas Turner, formerly the keeper of prints and drawings at the British Museum, as well as experts at Museo Ideale Leonardo Da Vinci in the artist's hometown of Vinci.

That brought the painting to attention of international experts, including Martin Kemp, of Oxford University, who is writing a book about the painting.

Kemp investigated figures surrounding Leonardo and surmised the painting was an enticement to marriage for Bianca Sforza, the daughter of Ludovico Sforza, Duke of Milan from 1452-1508, and his mistress Bernardina de Corradis.

Bianca Sforza would have been painted about 1496 by Leonardo, who also painted two of the Duke's mistresses, Kemp said.

At age 13 or 14, Bianca married the Duke's army captain, Galeazzo Sanseverino, a patron of Leonardo's, but died four months later.

The painting, which measures 33 by 24 cm, would be worth millions if accepted as being a piece by Leonardo.

It will go on display at an exhibit in Sweden next year.