As someone else said the piece is polished aluminum which is then anodized clear to protect the finish. If you strip off the anodizing and polish it eventually it will oxidize and dull.
So, the best thing is to buy a new piece or send your trim pieces to be stripped, polished and re-anodized. The company that does this is located in S. CA, called King of Trim. I used them to do 4 wheel well moldings on a 1969Firebird. Top notch work but expensive.
Check it out....
http://www.kingoftrim.com/home.html