Even More proving its mastery of chronographs and specifically higher-frequency precision, ZENITH unveils the DEFY El Primero 21 by using a new El Primero calibre beating at a phenomenal amount of 50Hz for an precise 1/100th of a next chronograph purpose. Tudor’s Black Bay line is on hearth with collectors. https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/