This story appears in the May 16, 2017 issue of Forbes.

The Bao Dai Rolex has a very conservative presale estimate of $1.5 million.

In 1954, Bao Dai, the last emperor of Vietnam, was in Geneva for peace talks when he excused himself to do a little watch shopping. The “Keeper of Greatness” selected a timepiece that lived up to his name—the most complicated Rolex made, a 6062 Oyster with a triple calendar and a moon phase.