Galvanized is to inhibit rust, but doesn't prevent it. Normally on roofing nails and such.
Galvanized steel is highly magnetic, and stainless steel, at least in the normal 300 series used for armor, is not, so that's an easy test if you have a magnet.
Also, be mildly careful with stainless steel - it CAN rust - it just takes a lot more for it to, well, rust, aka stain. Hence "stain less".
I'm not sure how to darken the finish, but my stainless steel IceFalcon voiders are dark, like Sir Edward's chausses - darker than my butter galvanized mail.