Calibre 2236 Is fitted which has a Syloxi hairspring that is made by Rolex and patented. This silicon hairspring provides a patented geometry that assures the calibre’s regularity in any place. 6 miles, or fifty five.7 km) at the conclusion of a six months’ voyage. (The geographical mile is defined https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/