Further Proving its mastery of chronographs and exclusively substantial-frequency precision, ZENITH unveils the DEFY El Primero 21 having a new El Primero calibre beating at a phenomenal price of 50Hz for an correct one/100th of the 2nd chronograph operate. This was the results of intensive R&D via the Manufacture, which https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/