Swiss. 40mm case diameter, circa 1991. The Rolex Explorer II was first released in 1971. It has carried on for 46 years as a robust, and functional extension of the original Explorer family. This Explorer II is an intrepid chronometer built to accompany explorers in extreme challenges. A distinctive red hand displays the time in 24-hour format to distinguish between night and daytime, even when journeying to the center of the Earth, through polar nights or sitting by a campfire. From a family Disney vacation to weekend camping getaway, to a night out, this is a versatile, functional watch. The original tritium number plots have taken on an impressive mustard patina. The watch was found to be running at the time of cataloguing. It has not been tested for timekeeping accuracy and may require adjustment.