A smudged fingerprint has convinced art experts that a painting thought to have dated back to the early 19th century is the work of revered Italian artist Leonardo da Vinci. It sold for $19,000 at the auction to respected New York art dealer Kate Ganz who kept it for 12 years before selling it on for a similar price in 2007. The work is now locked in a Swiss bank vault with an estimated value of more than $160 million.