The first-ever chronograph collection with a partially open dial revealing the beating heart of the movement returns in a new form. The Chronomaster Open is crafted with revised proportions in a 39.5mm case and even more openness on the dial. The Chronomaster Open offers a view into the high-frequency 5Hz regulating organ and escapement of the latest-generation El Primero automatic high-frequency calibre with a 1/10th of a second indicator.