The replica Rolex Cosmograph Daytona technically made its first appearance in 1963 as the Rolex Cosmograph. Decorated with a bezel engraved with a Tachymeter scale, the Cosmograph, or Le Mans, laid the foundation for what would later be famous as the fake Daytona sports watch. It wasn’t until after the replica Rolex became the official sponsor of the Daytona Speedway that the Cosmograph appeared with both the name “Daytona” on the dial and the Tachymeter bezel.
The Daytona has seen many bezel variations since its release, including stainless steel and plastic in early references and, more recently, aluminum, ceramic, and white gold. The Tachymeter bezel’s primary function is to measure average speeds per hour while traveling, a feature that was initially developed by Rolex in a bid to become the official replica watch of NASA, hence its original name “Cosmograph”. Instead, Rolex’s iconic chronograph found its home among the world of professional driving, with the Tachymeter bezel being used primarily to measure driving speeds.
Rolex has continued to improve upon the movement that powers the Daytona through the years, evolving from such movements as the Zenith “El Primero” calibre 4030 movement to the Rolex calibre 4130 movement, which is made completely in-house. The movement plays an important part in the accuracy of the bezel calculations.
At the very first beginning, unscrew both the top and bottom pushers. The top pusher will be used to start and stop the seconds-hand. The bottom pusher will be used to reset the display. Press the top pusher at the start of the distance that you wish to measure (such as a mile marker or the start of a lap around a racetrack); this will activate the chronograph’s seconds hand. Once finished, press the top pusher again to stop.
The average speed can now be read on the bezel. For instance, if you wish to calculate your driving speed over the course of 1 mile, press the top pusher to begin measuring. Once you’ve reached one mile, press the bottom pusher to stop. The number indicated next to the chronograph seconds hand on the bezel is your average driving speed.
You don’t need to be a NASCAR driver to make good use of the Tachymeter bezel. It can also be applied to measure the approximate time it takes to do anything over the course of an hour at an average rate.