So far, no counterfeit 146s as real piston fountain pens are known; with a 146 with a working piston mechanism (without unscrewable end cap for a converter), an original is therefore most likely to be assumed. For final certainty, one can present the pen to a Montblanc boutique, which is mostly free; sending in to service entails a service flat rate. With a stiff piston, professional servicing is recommendable; self-removal of the piston is, with the matching key, possible but is advised against for beginners, since the damage in case of error is high.