Let me talk about the case part (including the lug, crown, bezel and bottom cover). Generally speaking, the materials for making mechanical watch cases are as follows.
Stainless steel, this is the most common material used to make men's skeleton watches, which is what we call watches. In most cases, the stainless steel table is marked with "STAINLESS STEEL" or "STEEL", which means stainless steel. Most steel watches use 316L steel. The difference between the two is quite large. 904L steel has a higher nickel content, higher corrosion resistance, and is more comfortable and warm to wear. By the way, 904L steel is better than 316L steel. About three times more expensive.