The NCS homepage will tell you more.

I read the entry on a MS64FH SL quarter. I guess the graders at NGC felt the coin had some surface problems that held down the grade. Removal of these problems could increase the grade or help to preserve the coin at its current grade.

Here is the NCS page for their services and fees:

<a href="http://www.ncscoin.com/conservation/services_and_fees.asp">http://www.ncscoin.com/conservation/services_and_fees.asp</a>