Even Further proving its mastery of chronographs and particularly large-frequency precision, ZENITH unveils the DEFY El Primero 21 with a new El Primero calibre beating at a phenomenal rate of 50Hz for an precise 1/a hundredth of a 2nd chronograph purpose. Chronographs — with their bezels, scales and sub-dials — https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/