I went through this a few years ago.  Ended up using an abrasive loaded 
rubber disc on a dremel to 'sand' the silkscreen off.
(customer in the end did NOT want their name on the boards).  MEK, 
acetone, naptha, brake cleaner - none of those touched it.  NMP probably 
would work but that's nasty stuff.

Didn't look too horrible, but not pristine either.

For another board I mislabeled a connector - used white nail polish to 
paint over it but that took several coats to make it illegible.

Dave
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