On Thu, 16 Sep 2004 10:08:26 +0100, "jood"
It may well be bronze.
Copper is a pinkish red and weathers to either bright green or to a
reddish brown (depending on weather conditions), and eventually to
Brass and copper are easily distinguished. Brass is yellow, and
generally weathers to a dark gold. In extremis, it might be almost
black. With the right sort of corrosion, brass may "de-zincify" in
spots and turns pink, like copper (because that's what the spots are).
Bronze is harder to distinguish, because there are a range of
formulations for it, from almost-copper to almost-brass. Generally it
begins as a reddish brown and turns a dark brown or near-black. It's
almost indistinguishable from copper when weathered.
I'd expect you can tell brass and bronze apart pretty easily, even if
weathered. If they're really dirty, try making a tiny scratch with an
awl, penknife or small file.
Another way to tell (certainly in the UK) is that brass was usually
engraved and sometimes inlayed with coloured enamels. Bronze was
usually cast with raised letters.
I'd be surprised if your plaque is copper. Copper is quite soft and
bronze would be used instead.