Tail lights and park/turn lights housings Cuda -70

[Giveitawack]

The back of these housings has some kind of clear coat or mayby Cosmoline. Wax? Does not seem to be that affected by paint stripper. Tried acid, strong thinners. Some but not all goes away.
What is this coating and how can it be removed?

[mopardave]

they were a type of cad plating, you should be able to clean and paint over if needed.