The Big Blue earned its nickname rightfully. It’s large, chunky, bold, and, well…very blue. It is also important it is (maybe?) the world’s first self-winding diver’s chronograph, or so I understand. I’ve never been able to confirm that. I can confirm that it is the only Omega with either the cal. 1040 or cal. 1045 with a rotating bezel and screw-down crown. And after Omega stopped producing the Big Blue, they didn’t release another automatic diver’s chrono for about 20 years until the Bond-era Seamaster Professional chronograph.
Like the Mark III and the flightmaster, it is one of the quintessential executions of the Omega “pilot-style” helmet-shaped case. Omega referred to the shape as “anatomic” in that it was designed for comfort to conform to the shape of the human wrist. In addition to the rotating outer bezel (for timing dives), it has a blue inner bezel too (fixed with a minute track and numerals every 5 minutes). The crown is arch-shaped and screws in which was an advanced feature at the time. A true diver, the dial is covered with large luminous hour markers and the chronograph minute hand is a bright orange.
A Journey Through Time refers to the lume as tritium but the dial has no Ts outside of “SWISS MADE”. So it might be some other luminous material. Either way, the dial has a lot of it, which added to underwater visibility for the professional divers that used this watch as an actual dive tool.