How do you mark the 50th anniversary of one of the world’s most famous diving watches? If you’re IWC, you launch a limited-edition digital perpetual calendar that’s the first of its kind. The 49mm case is cast in matte-black Ceratanium – a bespoke material that took five years to develop, is as light and robust as titanium, and as scratch-resistant as ceramic. It also boasts self-correcting date and month indicators, a 68-hour power reserve, and the now customary in-house movement (this one a self-winding 89802 Calibre). The Aquatimer Ceratanium will go on sale in November, in a run of 50 pieces.