Even Further proving its mastery of chronographs and specially high-frequency precision, ZENITH unveils the DEFY El Primero 21 with a new El Primero calibre beating in a phenomenal charge of 50Hz for an accurate one/100th of the 2nd chronograph purpose. The expression “chronometer” took on a rather broader this means https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/