Further Proving its mastery of chronographs and especially superior-frequency precision, ZENITH unveils the DEFY El Primero 21 having a new El Primero calibre beating in a phenomenal price of 50Hz for an accurate one/100th of the next chronograph purpose. I bought a look at from Watches World and the process https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/