Omega. A fine and rare stainless steel “Staybrite” automatic diver’s wristwatch with sweep centre seconds

The Omega Automatic Seamaster 300 was “specially designed for professional and amateur divers”. Although originally guaranteed waterproof to a depth of 200 metres, the model was named “Seamaster 300” instead of “Speedmaster 200” because its performance was far beyond the capacities of the testing devices of the time. This outstanding result was essentially due to the high-resistance of the crystal and the “Naiad” crown.
See: Omega - A Journey Through Time, Marco Richon, p. 323.