Calibre 2236 Is equipped which has a Syloxi hairspring that is made by Rolex and patented. This silicon hairspring incorporates a patented geometry that assures the calibre’s regularity in any place. There you might have it, 5 brands that have played a tremendous position in the development of the chronograph. https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/