What's the difference between ACP, brass and stainless steel?

We offer three materials across the apartment and hotel door number range:

3mm ACP [Aluminium Composite Panel] - a real aluminium face, available in Matt Black, Matt White and Brushed Silver. Looks sharp and keeps the per-door cost down on larger projects.

3mm solid brass - water-jet cut from solid metal in brushed or polished finishes. Warm and golden, with the weight and presence to match. Brushed brass has a soft satin grain that hides fingerprints; polished brass is hand-finished for maximum impact in foyers and boutique settings.

3mm solid 316 stainless steel - all the weight of solid metal in a cooler, more contemporary tone, water-jet cut in brushed or polished finishes. Unlike brass it won't tarnish or develop a patina, and the marine grade makes it the pick for buildings near the coast.