Even Further proving its mastery of chronographs and precisely higher-frequency precision, ZENITH unveils the DEFY El Primero 21 by using a new El Primero calibre beating in a phenomenal rate of 50Hz for an accurate 1/100th of a next chronograph functionality. Tudor’s Black Bay line is on hearth with collectors. https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/