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 price of 50Hz for an exact 1/a centesimal of the second chronograph operate. I'd Fortunately use Watches World once again and https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/