More Proving its mastery of chronographs and specially significant-frequency precision, ZENITH unveils the DEFY El Primero 21 which has a new El Primero calibre beating at a phenomenal level of 50Hz for an accurate one/a hundredth of a 2nd chronograph perform. Tudor’s Black Bay line is on hearth with collectors. https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/