So what makes a Rolex Oyster an Oyster? The winding crown acts like a screw-on cap, or micro jar-lid, and has watertight gaskets in it. The best way to think of it is to imagine a submarine hatch that is threaded and has to be twisted or spun open or closed.
In 1926, at age 45, Hans Wilsdorf had successfully designed, manufactured and patented the waterproof Rolex Oyster. The challenge he faced was, how to communicate the value-proposition of such a product?
Hans came up with the idea of associating the fantasy of mermaids with the waterproof Rolex Oyster as seen in the 1926 French Rolex advertisement seen below.
1926 French Rolex Mermaid Oyster Poster