Further Proving its mastery of chronographs and especially superior-frequency precision, ZENITH unveils the DEFY El Primero 21 which has a new El Primero calibre beating at a phenomenal price of 50Hz for an accurate one/100th of a second chronograph purpose. Chronographs — with their bezels, scales and sub-dials — in https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/