Even Further proving its mastery of chronographs and specially superior-frequency precision, ZENITH unveils the DEFY El Primero 21 with a new El Primero calibre beating in a phenomenal rate of 50Hz for an accurate 1/one hundredth of the next chronograph operate. 1844: Adolphe Nicole introduces the reset aspect, allowing for https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/