1933 Henry Graves 'supercomplication' pocket watch, Patek Philippe

Sold for: $11 million at Sotheby's in 1999

Part of the legendary Henry Graves collection, the Supercomplication is the result of a race between Graves and his contemporary, James Ward Packard, to own the most complicated - with the most number of mechanical functions - watch. The watch took three years to build, and possesses 24 complications. It's also the most expensive watch ever sold at an auction.

Image courtesy: Reuters