Zenith ElPrimero
From Chronopedia
Zenith ElPrimero
The Zenith El Primero was introduced in 1969 and the first two versions were Caliber 3019PHC (with chronograph and date) and Caliber 3019PHF (with triple date, moon-phase, and chronograph).
This first automatic chronograph is a ‘fast ticker,’ with a frequency of 36,000 vibrations per hour (vph). Most chronographs at the time of its introduction were ticking at 18,000 vph or 21,600 vph. The 36,000 vph makes it possible to time intervals to 1/10th of a second.
