Further Proving its mastery of chronographs and specifically substantial-frequency precision, ZENITH unveils the DEFY El Primero 21 which has a new El Primero calibre beating in a phenomenal fee of 50Hz for an precise one/one hundredth of the 2nd chronograph purpose. Tudor’s Black Bay line is on fireplace with collectors. https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/