More Proving its mastery of chronographs and particularly superior-frequency precision, ZENITH unveils the DEFY El Primero 21 having a new El Primero calibre beating at a phenomenal price of 50Hz for an correct 1/one hundredth of the next chronograph operate. Thank you yet again for choosing Watches World! We keep https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/