Further More proving its mastery of chronographs and especially higher-frequency precision, ZENITH unveils the DEFY El Primero 21 using a new El Primero calibre beating in a phenomenal charge of 50Hz for an precise one/one centesimal of a second chronograph functionality. Impressed by British pilot’s watches through the 1970s, Hamilton’s https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/