Rolex takes its dedication to perfection in engineering capabilities, a step further by offering a more refined type of Stainless Steel in their timepieces. The 904L Stainless Steel they use, is referred to, as Oystersteel. It's been used in production since the early 2000s. Most other watch makers, use the industry standard, 316L Stainless Steel in their production. Both 904L and 316L are types of stainless steel commonly used in watchmaking and other industries. Here are some of the key differences between the two:

Chemical composition: 904L contains more chromium, nickel, and molybdenum than 316L. This gives it superior corrosion resistance and makes it more resistant to pitting and crevice corrosion in chloride environments.

Resistance to corrosion: 904L has higher resistance to corrosion in a wider range of environments, including seawater and acidic solutions, than 316L.

Hardness and toughness: 904L is generally harder and tougher than 316L, which makes it more difficult to machine and work with but also gives it superior durability.

Availability and cost: 904L is a more expensive material than 316L due to its higher content of expensive alloys, and it is also less commonly used. Therefore, 316L is more widely available and more affordable.

In summary, while both 904L and 316L are types of stainless steel used in watchmaking, 904L is generally considered to be a higher quality material due to its superior corrosion resistance and toughness, but it is also more expensive and less widely available than 316L.