Further Proving its mastery of chronographs and exclusively substantial-frequency precision, ZENITH unveils the DEFY El Primero 21 with a new El Primero calibre beating at a phenomenal amount of 50Hz for an precise one/one hundredth of a 2nd chronograph functionality. Chronographs — with their bezels, scales and sub-dials — in https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/