'Holy Grail' of watches set for November auction

The Henry Graves Supercomplication, a timepiece which has an estimated value of 12 million euros ($16 million), is "the most complicated watch ever made completely by human hand" and will be sold in Geneva on November 14, Sotheby's said.

"The list of superlatives which can be attached to this icon of the 20th century is truly extraordinary," the auction house said, describing it as "the Holy Grail of watches".

The timepiece, made by Swiss watchmaker Patek Philippe, was commissioned by prominent New York banker Henry Graves in 1925 and took a total of eight years to complete.

It features on its display not only the hour but also a plethora of other indicators: a perpetual calendar, the phases of the moon, sidereal time, indications for the time of sunset and sunrise, and the night sky of New York City, according to Sotheby's.

The Henry Graves watch was the world's most complicated for 56 years before it was surpassed by designs executed by technicians aided by computers.