Keyboard key tops show significant fingerprint "etching"

[Kaffimusic]

+1, looks like scratches, including maybe with some chemical burn involved. THE LAST thing I´d do is trying to clean it off with acid, which is vinegar. Best thing it can do is making things worse. NEVER EVER. When you want to clean and maintain plastics, use something like a cockpit cleaner for cars, which is essentially a fluid for plastics to clean and slightly seal. When I get hold of it, I use Armor All, but others will do as well. Acts to plastic like fat to leather - a bit. Spray on a soft cloth and rub the surface. It cleans it and makes plastics shiny again. Refreshes colour for weathered plastics as well, to some degree. But once the surface is scratched, it will stay dull.
I don´t know what you have done there, but it looks like it was hit repeatedly with something hard, like a ring or something. Fingernails do that after many month or years of use. They are usually too soft to hurt plastics that fast.