An extremely important white gold Patek Philippe single-button chronograph from 1928, undoubtedly the only one of its kind, is expected to fetch up to $2.7 million at Christie’s Important Watches sale in Geneva on May 16.

With more than 420 lots, the sale is expected to fetch a total of $14 – $19 million. The 1928 model is especially highly prized because so few watches of its caliber were produced during the Great Depression as demand waned. Nonetheless, Christie’s notes, even during the crisis an elite group of avid and demanding collectors continued to satisfy their craving for unique, super-complicated, custom-made watches such as the example on offer here.

Patek Philippe, in particular, produced some of their most beautiful and technically ingenious masterpieces during the Depression. Created in 1928 on the eve of the stock market crash, the 1928 chronograph was certainly made upon special request by one of Patek Philippe's most important patrons, though his exact identity remains clouded by time.

The cushion-shaped wristwatch, with vertically positioned registers and Breguet numerals, is the only known example extant of a single-button chronograph by Patek Philippe cased in white gold. As such, it’s perfectly possible that it could end up selling for more than $2.7 million, especially with the buoyant market for such horological masterpieces at the moment.