MP valve cover letter cleaning

[7DCUDA383A]

Was wondering if I can use fine grit sandpaper to clean the letters , my brother used a sand block on one of the letters and I told him to stop . My new MP air cleaner is new and the valve covers are darker , any suggestions would be appreciated.

 

[6PKRTSE]

Scotch brite A-Medium (Maroon/red-ish) hand pads work well.