Further Proving its mastery of chronographs and specifically high-frequency precision, ZENITH unveils the DEFY El Primero 21 with a new El Primero calibre beating at a phenomenal fee of 50Hz for an precise one/one hundredth of a second chronograph purpose. This was the result of intensive R&D with the Manufacture, https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/