Oystersteel is the name Rolex uses for the 904L stainless steel in its watches. Rolex makes this steel blend in its own foundry. It contains a lot of chromium and molybdenum, and it resists knocks and corrosion very well. Few other watch brands use this grade.
What is 904L steel?
904L is a high-performance grade of stainless steel. It is low in carbon and highly alloyed, which means other metals are added in large amounts. In 904L these include copper, chromium, nickel and molybdenum. Outside watchmaking, it is used mostly in the aerospace and chemical industries, because it resists corrosion so well. It is not the same as 316L, the steel that most other upmarket watch brands still use.
Why did Rolex switch to 904L?
Rolex dive watches were coming in for service with corrosion in the case threads and case backs. To deal with this, Rolex moved to 904L steel in 1985. The Sea-Dweller dive watch was the first Rolex model to use it. Other models followed, and by 2003 every Rolex steel watch was made from 904L. Rolex makes its own blend of the steel in its own foundry.
When did Rolex start using the name Oystersteel?
The name came long after the steel. Rolex first used the word Oystersteel in 2018, starting with that year’s new GMT-Master II watches. By then the brand had been using 904L since 1985. So Oystersteel is a newer name for a material Rolex already used: the same 904L grade, given a Rolex brand name. Steel Rolex watches made before 2018 do not carry the name, even when they are made from 904L.
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