Further Proving its mastery of chronographs and particularly substantial-frequency precision, ZENITH unveils the DEFY El Primero 21 with a new El Primero calibre beating at a phenomenal rate of 50Hz for an correct 1/a hundredth of a 2nd chronograph perform. Motivated by British pilot’s watches within the 1970s, Hamilton’s Khaki https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/