Further More proving its mastery of chronographs and specially higher-frequency precision, ZENITH unveils the DEFY El Primero 21 that has a new El Primero calibre beating at a phenomenal price of 50Hz for an correct one/a centesimal of the next chronograph functionality. I bought a view from Watches World and https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/