The spark test will help--SS sparks a little, brass not at all when touched to a grinding wheel.



Take a look at the ground surface, too. The brass will be yellowish, the SS shiny, steel-coloured. Also, a magnet may be faintly attracted to the SS...just faintly. This is hard to tell sometimes...I've seen the experts use a magnet dangled from a keychain so it is easier to tell if there is a faint attraction.

Jon.