If the note has a lacquer (prefix AOG 6M on), try a Q-Tip dipped in methanol (wood alcohol) or acetone (these solvents quickly evaporates) and rub gently with it while solvent-dampened. The ink should go off easily. without rubbing off the ink of the note, nor the lacquer itself. But it's possible that the stamp left a physical damage (with broken fibres, so the mark cannot be completely removed, it will be only less visible). If the note has not the lacquer, it will be more difficult to remove the ink completely because it will have penetrated more deeply in the paper, but it's not impossible. You will have to be more cautious. I suggest you to make some tests with an ordinary note (just ask a teller to stamp some notes...) before proceeding with this note.
But I'm optimistic because I already tried to mark a lacqued note with a permanent felt marker and then rinse with acetone and the ink was washed-off without leaving any trace. The same test on an unlacqued note left a trace of the mark.
Hope it will help...
