Even More proving its mastery of chronographs and precisely higher-frequency precision, ZENITH unveils the DEFY El Primero 21 which has a new El Primero calibre beating in a phenomenal price of 50Hz for an accurate one/a centesimal of a 2nd chronograph operate. This was the results of intensive R&D through https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/