Actually it's an annodized coating...You could possibly clean them up with a fine metal polish but you can't get too agressive you'll burn right through the coating...I've had a few that were perfect but the annodize coating got milky and would'nt clean up...I ended up stripping the coating off and polishing them up...Actually shines better than original and the aluminum used on those bezels were a high quality that only needs a small amount of attention each year...