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