Of the 142 from the 1950s no counterfeits are known, so on an heirloom or flea-market find an original is to be assumed. Replacement nibs are no longer kept by Montblanc for such old models; a matching nib change works only with an original 142 nib, alternatively a (more expensive) 132 nib. The change requires warming the barrel, unscrewing the grip section and pulling out feed and nib; from this beginners are urgently advised against, however, since the repair can damage the value of the writing instrument. Recommended are collectors' regulars' tables, specialist workshops or careful adjusting of the existing nib slit. The flat feed marks an early model variant with often more saturated ink flow but slightly increased leak risk.