I'd give TarnX a try. It should still be around somewhere. Maybe even at the local drug store. That will take the heavy discoloration off and then try Brasso or similar to polish it by hand.

I'll used that technique on old fire extingushers with very good luck

Frank
1956 Chevrolet 210 Delray Sedan
1963 VW Type 1 with 1600cc; slammed
1965 IHC with SBC and Turbo 350
19?? Tokheim 300