The Montblanc 121 was, according to the relevant literature (Collectible Stars by Stefan Wallrafen), made exclusively as a piston filler. A cartridge-filler variant is not documented; therefore the suspicion is close that it is a mixed assembly, e.g. with a body of a 220 and a cap from the 121. A counterfeit is with these editions practically ruled out, since they are uninteresting for counterfeiters. Ultimately the variant remains difficult to unambiguously assign.