The Word of the Day: OYSTER

In 1926 Rolex creates the first really waterproof case in the world. The famous OYSTER is born.

This registered name is a synonym of the watertight closure, which works in and out of water preventing the penetration of impurities, moisture, dust, ...
The Oyster watch combines an extremely sturdy case, with a case back and a winding crown, all absolutely waterproof. The patented TWINLOCK winding crown, is wound against the case and makes this generally very vulnerable point of the watch, extremely resistant.

From a Rolex catalogue of 1981 we can read:
OYSTER
The Oyster is perfectly at home underwater.
For Rolex, the word Oyster is a symbol as well as a registered trademark. All Rolex
Oysters are guaranteed waterproof up to a depth of at least 50 m. This guarantee is extended to 100 m for the Explorer, to 300 m for
the Submariner and to 1220 m for the Sea-Dweller with helium escape valve (Rolex patent).

From a Rolex catalogue of 1992, instead, we can read:
OYSTER
The Oyster, true to its name, is perfectly at home underwater.
For Rolex, the word Oyster is a symbol as well as a registered trademark.
All Rolex Oysters are guaranteed waterproof up to 100 m. This guarantee is extended to 300 m for the SUBMARINER, and to 1220 m for the
SEA-DWELLER, with helium escape valve. The Oyster case was invented and patented by Rolex in 1926.

Complete information about Rolex Oyster in the books:

100 Years of Rolex

Collecting Modern and Vintage Rolex Wristwatches

Rolex Gallery