I have seen brass, aluminum and lacquer and plated (zinc) steel cases. They are very easy to tell what the base material is. Never saw a "plated" or painted aluminum case. I've seen very few brass plated steel (99.9% of all the steel cases I've shot or seen at the range) and most are galvanized/zinc plated or painted. I've shot a lot of 5.45x39, 7.62x39 and some 9mm imports, three or four different manufacturers, but none have been brass plated....