I've noticed that some K-31's don't have the electropenciled CAI number on them, while mine does. It irritates me as much as engraved safety warnings. It's not the serial number. Before I have the metal re-blued, would I be commiting a no-no by carefully grinding off the electropenciling, and getting it back to the way it was in 1942? Is it proof of importation date, and if so, is that why there are some without this grafitti?