Calibre 2236 Is fitted which has a Syloxi hairspring that is made by Rolex and patented. This silicon hairspring includes a patented geometry that ensures the calibre’s regularity in almost any posture. Numerous of their versions are available in the two quartz and computerized versions, naturally at unique cost factors. https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/