Further Proving its mastery of chronographs and specifically high-frequency precision, ZENITH unveils the DEFY El Primero 21 which has a new El Primero calibre beating in a phenomenal charge of 50Hz for an accurate one/one hundredth of the next chronograph purpose. Chronographs — with their bezels, scales and sub-dials — https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/