Calibre 2236 Is equipped which has a Syloxi hairspring that is produced by Rolex and patented. This silicon hairspring provides a patented geometry that ensures the calibre’s regularity in any place. Coupled with his colleague Thomas Earnshaw, the pair would establish simplified and simple maritime chronometers. In Doxa's modern assortment, https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/