Even Further proving its mastery of chronographs and particularly significant-frequency precision, ZENITH unveils the DEFY El Primero 21 using a new El Primero calibre beating at a phenomenal level of 50Hz for an precise one/100th of a second chronograph purpose. Thank you yet again for choosing Watches World! We continue https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/