Further Proving its mastery of chronographs and especially higher-frequency precision, ZENITH unveils the DEFY El Primero 21 which has a new El Primero calibre beating in a phenomenal price of 50Hz for an correct one/one centesimal of the next chronograph function. This was the result of intensive R&D from the https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/