filed off the serial numbers

Verb

file off the serial numbers (third-person singular simple present files off the serial numbers, present participle filing off the serial numbers, simple past and past participle filed off the serial numbers)

1. (idiomatic) To alter identifiable details in a creative work in order to conceal its origin.
   • […] that song belonged to Noisy when he got through filing off the serial numbers and changing the body lines. I heard it again, oh, must have been twenty, twenty-five years later, in a cabaret in Luna City. From Noisy. But he had changed it. Fixed up the scansion, given it a proper rhyme scheme...1973, Robert Anson Heinlein, Time Enough for Love
   1. (idiomatic, slang) Especially, to remove the copyrighted elements from an existing work of fan fiction so that it may be commercially published as original fiction.
      • For a while now, I've been pottering away at a Star Wars fanfic novella ([URL redacted], if you must know). I've received a few pokes about filing off the serial numbers and trying to sell it as an independent work.1998 March 6, Julie Lim, “Help!”, in rec.arts.sf.composition (Usenet)