Most Meisterstück pens carry the laser engraving “Germany” on the clip. A French marking is no anomaly, however: the caps and bodies of certain editions, notably various Meisterstück Solitaire versions and some Bohème editions, really were made in France. Montblanc does not manufacture every part itself but can draw on numerous production sites within the Richemont group, to which Cartier also belongs. For a time the Solitaire sleeves were produced in Pforzheim as well.
Such pieces are accordingly fewer in number than the line's total output, but that does not make them rarities; where the metal parts were made has no discernible effect on collector value. The claim that French-made parts are finished to a “higher” standard is wishful thinking too: every supplied part has to meet the same quality requirements, and the overlays made in France are in no way inferior to those from German production.
Listings that turn the “France” engraving into particular rarity or a price premium therefore have nothing to support them.