More Proving its mastery of chronographs and precisely high-frequency precision, ZENITH unveils the DEFY El Primero 21 using a new El Primero calibre beating in a phenomenal level of 50Hz for an exact 1/a centesimal of a second chronograph function. The expression “chronometer” took on a rather broader indicating as https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/