Further More proving its mastery of chronographs and specially superior-frequency precision, ZENITH unveils the DEFY El Primero 21 with a new El Primero calibre beating at a phenomenal rate of 50Hz for an accurate one/one centesimal of the 2nd chronograph function. Encouraged by British pilot’s watches within the 1970s, Hamilton’s https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/