years ago (it must have been at Motorfair '84?) I saw a 'chroming fluid' for use on brass or copper IIRC (but they may have said steel.) Anyway, the guy demonstrated it and it looked perfect. I passed him a 2P coin, and he treated 1/2 of one side. I kept this 2P rattling around in my loose change for months, and alas I must have inadvertently spent it one day
In all the time I had it the chrome finish looked perfect - I wonder if anyone still sells it?