On my bike the paint was chipping off from the chromed parts (which I did not know were chrome). Underneath the paint was a greyish layer sort of like the picture of the rear dropout on yours. The greyish layer turned out to be a gummy substance that I suspect was used as a sort of primer when they painted over the chrome. May be worth scraping off a tiny bit of the greyish stuff to see what is underneath. I mostly used a razor blade with a very light touch.

Restoring chrome under paint?