Further More proving its mastery of chronographs and specially substantial-frequency precision, ZENITH unveils the DEFY El Primero 21 which has a new El Primero calibre beating in a phenomenal charge of 50Hz for an accurate one/one hundredth of a 2nd chronograph functionality. The Speedmaster will get the many like in https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/