Calibre 2236 Is fitted which has a Syloxi hairspring that is made by Rolex and patented. This silicon hairspring contains a patented geometry that makes certain the calibre’s regularity in almost any position. ZENITH launches the 135-Observatoire restricted edition, generating the acclaimed 135 calibre, serial winner with the international Chronometry https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/