It's aluminum. If it's faded, it's a simple fix with any good aluminum polish. Polished aluminum DOES lose it's lustre...because it's basically untreated and the acid in your skin will fade the finish. It will even oxidize on its own after a period of time.
Like I said, any decent aluminum polish and a Q-tip/ cloth will restore the original lustre easily. Just be careful not to rub the polish on the painted surface or the glass. It will wear out the paint and then you'll have to buff the entire painted surface to remove the paint...
If you hit the glass with it, it will scratch the glass
You can use:
Mothers
McGuires
Autosol
There are a ton others out there, but these three work well and are the more recognized and more easily available brands...