Bezel marker discoloration on ceramic sub

[rmar20019]

Hello all

Ive got this wierd smudge on the 35 bezel marker. Im not sure what it is; I bought it this way without noticing. I have tried to clean the bezel with some dish soap and a soft tooth brush, but the mark didn't come out.

Some of the other markers have some similar discoloration in the middle.

Has anyone here had a similar issue? If so, how do I clean it, if possible?

Thank you in advance!