Additional Proving its mastery of chronographs and particularly high-frequency precision, ZENITH unveils the DEFY El Primero 21 using a new El Primero calibre beating at a phenomenal level of 50Hz for an accurate one/one hundredth of the next chronograph perform. Encouraged by British pilot’s watches within the 1970s, Hamilton’s Khaki https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/