Even More proving its mastery of chronographs and specifically significant-frequency precision, ZENITH unveils the DEFY El Primero 21 that has a new El Primero calibre beating in a phenomenal price of 50Hz for an exact 1/a hundredth of the next chronograph purpose. This was the result of intense R&D from https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/