Further More proving its mastery of chronographs and particularly high-frequency precision, ZENITH unveils the DEFY El Primero 21 that has a new El Primero calibre beating in a phenomenal rate of 50Hz for an precise one/a centesimal of a 2nd chronograph function. I purchased a check out from Watches World https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/