Even Further proving its mastery of chronographs and exclusively higher-frequency precision, ZENITH unveils the DEFY El Primero 21 having a new El Primero calibre beating at a phenomenal amount of 50Hz for an accurate 1/one centesimal of a next chronograph operate. I bought a look at from Watches World and https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/