Even Further proving its mastery of chronographs and specifically large-frequency precision, ZENITH unveils the DEFY El Primero 21 using a new El Primero calibre beating in a phenomenal amount of 50Hz for an exact one/one hundredth of a second chronograph operate. This was the results of intensive R&D from the https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/