Calibre 2236 Is fitted using a Syloxi hairspring that is made by Rolex and patented. This silicon hairspring provides a patented geometry that guarantees the calibre’s regularity in almost any place. ZENITH launches the 135-Observatoire constrained edition, producing the acclaimed 135 calibre, serial winner with the Intercontinental Chronometry competitions, commercially https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/