Further More proving its mastery of chronographs and precisely superior-frequency precision, ZENITH unveils the DEFY El Primero 21 using a new El Primero calibre beating at a phenomenal level of 50Hz for an exact 1/a hundredth of the next chronograph functionality. Impressed by British pilot’s watches through the 1970s, Hamilton’s https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/