Battery cap tarnish or fading issue?

[gobookee]

My 5V HP ST is having a cosmetic issue.....
i noticed that the battery cap is changing colors..... espeically where i grip it to vape....
what can i do or use to get rid of the tarnishing and get the shine back??

 

[Sir_Lawrence]

If you have a Brass cap... tape of just under the top cap with very low tack painter's tape and use a tiny bit of Brasso on it.
If you have a Nickel Plated cap, use a little jewelry cleaning paste, very lightly so as to not wear off the nickel plating.