For the plain production models of the 1950s and 1960s, recognisable by the two-digit model number on the cap ring such as 21 or 31, Montblanc no longer keeps replacement nibs; as a rule the factory service is no longer an option for these pens. The work is done instead by dealers and nib workshops specialising in vintage writing instruments. In the German-speaking countries Interpens and Maxpens are among the well-known addresses; they carry suitable nibs from old stock and rework existing ones.
Before placing an order it is worth asking whether the existing nib can be saved: a worn or unevenly run-in tip can often be reground, which costs less than a replacement and preserves the pen's originality. Financially, the matter deserves a sober look, because on the two-digit models proper nib work can amount to a substantial share of the market value. Where a pen has personal associations, experience shows that this counts for nothing. An estimate in advance is advisable in any case.