Renamed “Big Crown” by collectors, an allusion to its 8 mm winding crown, reference 7924 appeared in 1958. At first glance similar to its predecessors, it presented a fundamental innovation in that its waterproofness was from then on doubled to a maximum immersion depth of 200 metres.
To reach this new threshold, the Submariner case, 37 mm in diameter, had been made thicker and was equipped with a larger screw-down crown. A new Tropic-type Plexiglas crystal, thicker and dome-shaped, was installed for better resistance to great pressure.
With the same self-winding calibre 390 as reference 7922 at its heart, this new Submariner bore at 6 o’clock on its black lacquered dial the inscription “200 m = 660 ft”, a reminder of its waterproofness guarantee. Its hands reverted to the characteristic Submariner design. Its Oyster-type bracelet with riveted links, reference 7206, bore the Rolex signature.