1974 Sicura Submariner 400 meters.
Sicura Vaccum Tested, manual winding movement cal. SIC 19, 38.4 mm. case., popularly called Sicura Submariner.
Sicura was a company owned by Ernest Schneider, specializing in big sports watches of innovative design in the 60s 70s. Sicura was able to purchase Breitling when it went into receivership in 1979 and remains the current owner.
The first ever specialized diving watches were the Panerai, used by the Italian frogmen in the Second World War. Actually, they were Rolex 3646s with special dials made by Panerai.
Right after WWII, two French combat diving corps started to search for a military grade diving watch, big and easy to read underwater, hermetically sealed and capable of absorbing shocks this helped Blancpain to develop the legendary Fifty Fathoms introduced in 1953. The transformation of the simple water resistant watch to the tool diver watch happened at that exact point. The next year Rolex launched perhaps the most famous diver watch of them all, the Rolex Submariner; from that point most of the Swiss companies started to shift their attention towards the sea, trying to produce reliable underwater-capable wristwatches.