Originally Posted by
70SATMan
If it's matte, then I suspect oxidation. It happens with the aluminium coatings. Similar to reflectors on light units like our TTG lights, fog lights and headlights. When first made, I'm sure it was shiny.
Don't try to manually polish it, it's so thin that you'll go through and just make it worse. One trick I used to use on light reflectors was a solution of isopropyl alcohol with just a little salt added. I would swirl the solution around in the reflector and empty. Not 100% back to original but, usually a solid improvement. The grains of salt provide the barest of abrasion to remove the oxidated layer. Better than using paint or chroming. Chrome is actually one of the worst things. It's far less reflective than one would think.