Further More proving its mastery of chronographs and especially significant-frequency precision, ZENITH unveils the DEFY El Primero 21 with a new El Primero calibre beating at a phenomenal fee of 50Hz for an exact 1/one hundredth of the next chronograph function. I might Fortunately use Watches World yet again and https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/