Additional Proving its mastery of chronographs and particularly substantial-frequency precision, ZENITH unveils the DEFY El Primero 21 which has a new El Primero calibre beating at a phenomenal amount of 50Hz for an accurate 1/a centesimal of a second chronograph operate. Chronographs — with their bezels, scales and sub-dials — https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/