Rolex Bubbleback ref. 2940

In the 1920s, numerous watch-making companies were trying to create a self-winding movement. They kept attempting to incorporate slight modifications to Harwood's self-winding watch that featured a no winding stem. However, Rolex was following altogether a different path. It experimented with its existing movements and looked for a new solution to the old challenge. Finally, in 1931, Rolex created the Auto-Rotor movement from an existing Aegler movement (subsidiary seconds Hunter 8-3/4"). This invention resulted in a "perpetual motion" wherein the winding mass could turn smoothly both clockwise and counter-clockwise and pivot a full 360 degrees on its staff in the center of the movement. In 1932, Rolex patented its first successful self-winding perpetual wristwatch. One year later, the Rolex Bubbleback was introduced into the market. Due to unsuccessful attempts in the past and the resulting skepticism in the public eye, Rolex tried to publicize this new model as "the watch sensation of 1934".