Even More proving its mastery of chronographs and specially large-frequency precision, ZENITH unveils the DEFY El Primero 21 that has a new El Primero calibre beating at a phenomenal amount of 50Hz for an exact 1/one hundredth of a 2nd chronograph functionality. This was the results of intense R&D with https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/