If you're interested in a dive watch with industrial strength, professional capabilities but you'd like a more classic size, then the 40mm Rolex Sea-Dweller, ref. 116600 is the kit for you. Released at the 2014 Baselworld Fair this watch became an instant classic among Sea-Dweller aficionados because it returned to the longstanding 40mm case size, which is something that hadn't been available since 2008. Like all Sea-Dwellers it only comes one way (and never in precious metal or two-tone): 40mm brushed stainless case with matching Oyster bracelet, helium escape valve, screw-down Triplock crown, black "maxi" dial with Chromalight lumed hour markers and Mercedes hands, Rolex patented black Cerachrom ceramic bezel and the standard Sea-Dweller small date at 3 (sans cyclops). The text is white, which is how its been for every Sea-Dweller since the late 1970s. Using the in-house Rolex automatic caliber 3135 - which is also used in the Submariner - the 116600 really is a return to the classic Sea-Dweller loved by so many. Even the depth rating was returned to the standard 1,220 meters/4,000 feet, as it had been since 1978. Overall, one of the things that makes the Sea-Dweller so great is that is was purposely built to solve a rather significant issue at the time. In the mid-1960s the US Navy, Jacques Cousteau and the Compagnie Maritime d'Expertises (COMEX) company were all separately developing deep water saturation diving techniques when COMEX came to Rolex with a problem: accumulated helium at depth was causing the crystals of their Rolex Submariners to pop off during decompression, which obviously isn't acceptable. Rolex responded by developing and then fitting a one-way helium escape valve to a handful of COMEX Subs but instead of forever modifying the Submariner line Rolex just made a brand new watch for brand new professional needs, a la the Sea-Dweller. It had a beefier case, thicker crystal, greater depth capability, helium valve, etc, which has been its m.o. ever since. This 116600 is a terrific watch that's depth-rated the same as the brand new 2017, 43mm Sea-Dweller but with a case size that's 3mm smaller. Now that its been discontinued in favor of the larger pieces its only available on the secondary market, which means this piece will always hold a unique place in the hearts of the Sea-Dweller enthusiasts and it's as professional as every Sea-Dweller before it so there's no compromise. It's a perfect watch.