Can anyone explain what accounts for the differences in color/tone of the stainless steel used for various watch cases and bracelets? My quick search did not turn up any posts on this topic. What I'm referring to is different shades of steel color. I don't mean the lustre - as I understand it, that refers to the level of surface reflectivity caused by different types of finishes, such as brushed vs. satin vs. polished. (As with semi-gloss vs flat paint.) As an example, my Sinn 556i appears noticeably lighter or brighter than my Archimede Outdoor Protect. (Both are on their original bracelets.) The Sinn has a more lustrous satin finish, while the Outdoor is finely brushed. But the actual color of the steel itself looks different. Could this be due to different grades of steel being used, such as 304 vs 316? The case, but not the bracelet, of my Outdoor has been hardened, but both case and bracelet are the same shade. Any metallurgists out there who can shed some light on this?