Here’s the before and after pictures of a microscope I have just finished, a Beck folding binocular microscope. It wasn’t in terrible condition but where it may have got damp at some point because the metal was quite pitted, especially where the lacquer was lost.
Here is the same microscope afterwards, the dark patches are gone, as are the green patches of corrosion. It hasn’t lost all signs of age but it looks much better than it did. The stage clips and the edges of the fine focus knob have been silvered