As far as brass vs nickel on the snaps, when I started more than 50 years ago the difference was the agency and color of the uniforms; we wore navy blue with black basket-weave leather and brass snaps. The county wore tan, and later green uniforms with black basket-weave with nickel snaps (and of course, the Sam Browne buckle). We certainly envied them the snaps that did not require polishing.