Further Proving its mastery of chronographs and particularly substantial-frequency precision, ZENITH unveils the DEFY El Primero 21 having a new El Primero calibre beating at a phenomenal amount of 50Hz for an accurate one/100th of the 2nd chronograph functionality. Thanks yet again for selecting Watches World! We remain at your https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/