Calibre 2236 Is fitted which has a Syloxi hairspring that is made by Rolex and patented. This silicon hairspring provides a patented geometry that makes sure the calibre’s regularity in any situation. In the meantime, Graham has also ventured beyond their ease and comfort zone with some bigger echelon pieces. https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/