Copper or Bronze

Hi,

Does anyone know how to differentiate between copper and bronze on old coins.

Specifically, whether Une Centime l'an 6-8 is copper or bronze as different catalogues give opposing answers.

For example Gadoury says Bronze whereas Le Franc says copper.

Angus

One can add brass to the mix...

If you search for

copper bronze brass

in Google, you will find many pages explaining the differences. Copper is a metal and ... 100% copper. Bronze and brass are alloys mostly made of copper (well over 80-85%) with a small part of tin, zinc, &/or other metals.

Catalogues often say "bronze" where "copper" is meant. For example, catalogues and collectors often say that the US large cents were made of bronze, but they were actually made of pure copper.