Art Deco and Good Books on Antique Brooches by: Leigh Leshner
Metals in Art Deco Brooches look very different based upon the type of metal used. Pot metal appears dull, rhodium appears shinier and other metals will vary in appearance, based upon the mixture of metals used.
There are books that show examples of the different types of metals that would be helpful, like the one here. Just because a metal is shiny does not mean that it is rhodium, so you need to look at books and real examples to see the differences.