More Proving its mastery of chronographs and specifically superior-frequency precision, ZENITH unveils the DEFY El Primero 21 having a new El Primero calibre beating in a phenomenal price of 50Hz for an precise 1/100th of the 2nd chronograph function. The Speedmaster gets each of the like in Omega’s chronograph lineup, https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/