Every Rolex that's signed 'Rolex' (the Cellinis don’t count here) carries the moniker 'Oyster Perpetual' these days. Even if they’re not specifically the Oyster Perpetual models. So what does Oyster mean anyway? And where did it come from?
Well, the urban legend (the one you’ve probably heard) is that Hans Wilsdorf used the term ‘oyster’ for his cases because he perceived that a real oyster was so tight, debris from the sea floor couldn’t get inside the shell. That’s what he wanted for his watch cases – nothing getting inside to gum up the works, as it were.
And the legend is probably mostly true. Certainly Rolex released the Oyster case – screw-down crown, bezel, and case back – in 1926. Did you know the origin of the flutes on the fluted bezels was as a gripping surface for the tool used to unscrew the bezel? The screw-down bezel is gone now, replaced by a tight press-fit bezel which serves to capture the crystal in a friction fit and helps promote water resistance. But the screw-down case back and crown are staples of water resistant watches everywhere, not just with Rolex.
Rolex filed a patent in Britain in 1926 for the oyster case, just before releasing watches which used the system. This patent filing followed Wilsdorf’s acquisition of a 1925 patent filed by Paul Perregaux and Georges Peret in Switzerland. Wilsdorf saw the advantages of the design right away and negotiated with Perregaux and Peret for the rights.
Perregaux-Perret Patent, 1925
All this happened after previous, less successful attempts by Rolex to create a water-tight case. Several unnamed case manufacturing firms were used with less than spectacular results. This resulted in Rolex sourcing cases from Dennison in Britain in 1915, right after WW I started. Dennison’s first case went a long way in fighting infiltration by dust and water, and several evolutionary improvements were made before the Perregaux-Peret patent filing and subsequent acquisition.
Wilsdorf's Screw-Down Crown, 1926
And even after Rolex began using the acquired patent design, they continued refining and improving it. This of course, has become a habit with Rolex.
Rolex Deepsea Ringlock Patent Illustration
In fact, the design has barely changed at all conceptually since the screw-down bezel was eliminated. Mechanical design changes have been made, but rarely have components been added or taken away. An exception might be the Sea-Dweller Deepsea and its Ringlock system screw-down case back. But conceptually, that system varies only slightly from the original oyster concept.