Calibre 2236 Is fitted using a Syloxi hairspring that is made by Rolex and patented. This silicon hairspring features a patented geometry that makes certain the calibre’s regularity in any posture. There you might have it, 5 brands that have played a big role in the development of the chronograph. https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/