The 164 is the ballpoint of the Meisterstück line and has been in production for decades; coloured versions such as the red one typically date from the 1990s. The model 1876 is a gold-coloured writing instrument made between roughly 1971 and 1975. Very slim black-and-gold pens with a narrow clip can often be assigned to the Noblesse line, though a firm identification calls for examining the piece itself, since photographs render imprints, hallmarks and transitions poorly.
An engraved dedication or company anniversary reduces the collector value considerably. An engraving can only be removed by taking off material, which damages the contour and the gold plating and is impossible altogether where the plating is thin; attempting it yourself is not advisable. If you need a binding valuation, for probate or for insurance, go to a dealer who specialises in Montblanc. Stefan Wallrafen, among others, offers appraisals; the pens have to be sent in, and the valuation is chargeable.