Interesting. I've spoken to a few local platers and they have suggested either gold or brass plating. Zinc Dichromate is more of a "dull" finish that is used for nuts and bolts. Maybe this is what the finish originally was ? So I'm told, the finish is not as polished as gold or brass, but it will have a "rainbow" effect through the surface.

I'm dropping into Preston Platers this week to see what I can learn about it and then I'll look at my options. Seems they already do work for pinball enthusiasts !