Rolex began using 904L stainless steel for its watches in 1985. The alloy became one of the company’s distinctive material choices, replacing the more commonly used 316L stainless steel in many Rolex cases and bracelets.
904L steel is highly resistant to corrosion, an important advantage for watches exposed to sweat, salt water, humidity, and everyday chemicals. Rolex also emphasizes the bright, attractive finish the alloy can take after polishing. However, 904L is not simply “better” in every practical sense: it is more difficult to machine and can be softer and easier to scratch than 316L steel.
The date is often mixed up with later uses of other Rolex materials. Cerachrom ceramic bezels, for example, arrived much later, beginning with the GMT-Master II in 2005. Likewise, specific models may describe the alloy as Oystersteel, Rolex’s name for its corrosion-resistant stainless-steel material. The underlying 904L choice dates to 1985.