I have the most divine Montblanc 146 G, vintage approx 1960's.
I am curious as to the significance of the letter 'G' after the model number 146.
Is there a plain 146, without the 'G' or what?
Any knowledgeable MB scholars able to satisfy my curiosity?

As a Mont Blanc collector - but no expert - I will gladly stand corrected regarding my answer.

First, your 146 is older than 1960's. The 146 production stopped about 1959, when MB went to the two-digit numbering system and the "space-age" look with Meisterstuck 12 & 14 models. The "G" on your filler knob indicates a 1950's production. The G indicated that the nib was gold rather than alloy. During the war and subsequent recovery years, many MBs and Pelikans were marketed, at least domestically, with alloy nibs. The "G" eventually disappeared, but I'll leave that date to the real experts.