I have an old-ish guitar which, I hasten to add, I came by legitimately.

The serial number, which would have been printed on a paper label, has been erased. The label is intact but the surface looks roughened on the three relevant lines.

Any suggestions how I (or anyone more expert) might be able to read the erased number? I have tried the ultra-violet light used to test banknotes, and it does not help.