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