This Rolex Sky-Dweller reference 326938 is the brand's most mechanically ambitious travel watch, pairing a second time zone with an annual calendar in a format unique within the modern Rolex line. Its automatic caliber 9001 was developed for the model, with the Saros annual calendar and off-center 24-hour display making this the watch for a collector who wants Rolex at its most technically involved. The annual calendar absorbs the date within a more complex whole, and in the Sky-Dweller it is resolved with the directness that defines the reference. In 18k yellow gold the case measures 42mm across and 14.1mm thick, giving the watch the scale that suits its complication set without losing the balance expected of a Rolex case. The silver dial keeps the display unusually clear for a watch carrying this much information. Within the brand's catalog, the Sky-Dweller stands apart as the point where Rolex moved beyond the usual tool-watch brief into something distinctly more complex.