Further More proving its mastery of chronographs and especially superior-frequency precision, ZENITH unveils the DEFY El Primero 21 using a new El Primero calibre beating at a phenomenal charge of 50Hz for an accurate 1/100th of a next chronograph purpose. Motivated by British pilot’s watches in the seventies, Hamilton’s Khaki https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/