A 146 with a continuous, unribbed ink window typically dates from the 1980s. The nib gives a further pointer: two-tone nibs, that is gold nibs with a rhodium-plated panel, only appeared at Montblanc at the start of the 1990s. If a pen from the 1980s has such a nib, it was fitted later, usually in the course of a repair at the factory. That is not a defect and does not affect use, but it should be taken into account when valuing the pen as a collector's item.
Matching companion pieces were available in the 1980s in one size only, namely the ballpoint now listed as the Classique 164. Since the 146 has borne the name LeGrand, Montblanc has offered companions of the same size: the 161 ballpoint and the 167 propelling pencil. If you are after a set of fountain pen, ballpoint and pencil that looks all of a piece, take those two; if you prefer the slimmer shape in the hand, stay with the 164. In period terms the 164 is in any case the better match for a pen from the 1980s.