A pen like that is simply a Meisterstück 146. The name LeGrand came in only during the 1990s, when Montblanc reorganised the sizes within the line: the barrel of the 147 Traveller had to be lengthened so that two cartridges would fit, and the 146 was brought into line with it. Only in that context did the remaining LeGrand writing instruments appear — ballpoint, propelling pencil, rollerball and document marker in the matching size.
Before that there was no such correspondence. The ballpoint that went with the 146 in those days was the 164, which was not yet called Classique either. There is nothing odd, then, about a LeGrand ballpoint 161 measuring just under 148 millimetres and so coming out a few millimetres longer than an eighties 146 at around 142 millimetres; it is no sign of a wrong or foreign part. The diameter of about 15.5 millimetres is the same on both. The single-colour 14-carat nib likewise fits that production period.