Copper alloy or bronze?
Why cataloguers say “copper alloy”.
Without analysis you usually can’t tell bronze (copper + tin) from brass (copper + zinc) or gunmetal (copper + tin + zinc) by eye. “Copper alloy” is the honest, standard term, and it is what museum catalogues use for exactly this reason.
Colour is a weak guide — surface corrosion masks the metal beneath, and many ancient alloys also carry lead, added to make the melt pour better. Record what a fresh break or an old scratch exposes, but don’t over-claim from it.
The reliable answer is instrumental: an XRF reading gives the actual composition in seconds, and some museums and finds officers can arrange one. Until then, the alloy is a guess.
Reserve “bronze” or “brass” for when you have a real analysis to cite. An honest “copper alloy” never has to be corrected later.