Other than “compound” like what’s used on car paint, I don’t really have any ideas if solvents, etc., don’t wipe it clean.
Still, does it really make that much of a difference? I take care of my lights and keep them clean, but some pocket-carry lights I have, have gotten so jostled with keys, loose change, etc., that now they look like bobofett’s helmet.
To me, means they’re well-worn and well-loved. 
Haha, not much difference, that’s true. Aside from AA-powered edc lights carried in a holster and gets beaten up day in and day out, all my other lights, including this only light that suffered from this dark spots, just stay inside their original boxes.
I would try some lacquer thinner or acetone. If those don’t work then try rubbing the whole light with mineral oil. Solvents don’t hurt type 2 matte anodizing.
Looks like wax on a matte surface. Heat can help remove it. Heat it to 50+ degrees Celsius and wipe it with a cloth. See if anything changes.
Did you put the hot (37+ degrees is wax melting temperature) light close to a candle or waxed surface?