Calibre 2236 Is fitted which has a Syloxi hairspring that is made by Rolex and patented. This silicon hairspring contains a patented geometry that guarantees the calibre’s regularity in any place. six miles, or 55.seven km) at the end of a 6 months’ voyage. (The geographical mile is defined as https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/