In production between 1933 and 1955. Caliber 1600, Rolex first self-winding movement. Beware of the reverser/clutch wheels. They have some very fine teeth and a stopper “knife” that is hard to repair. Otherwise, solid as a rock and probably still to a degree water resistant (or as Rolex used to say on the old hang tag - swimpruuf).
Also pay attention to a nice detail, the beautiful blued seconds hand.