For this particular piece the value is in the design whether or
not precious metals are used... I am wanting to find a combination
of two differently coloured metals to use for the piece. A high
priority is tarnish resistance.
As I've mentioned in previous discussions regarding tarnish and base
metals, I get good results with brass and copper using a patina
solution containing selenous acid (e.g., Jax-Black). I rub off the
excess with damp pumice. At least with my skin, I no longer get
any green patches. Brass and copper produce a very nice color
contrast, especially when they do not have a mirror finish and the
recesses of the design are shadowy from the patina.