Three checks expose a great many fakes without any specialist knowledge at all. First, the star: Montblanc's emblem is white. A black star, or one in any other colour, on the cap top as much as on the packaging, is a certain mark of a fake; boxes with a black star do not come from Montblanc. Second, the lettering: genuine pens and their packaging carry the full name “Montblanc”. Abbreviations or variants such as “mont” are typical of the counterfeit market, where near-brands of this kind are sold in quantity.
Third, the model itself: if a supposed Montblanc product cannot be traced in any catalogue or model listing, the question has usually answered itself, because many of the combinations of pen, pouch and box sold as Montblanc were never made by the company at all. Pieces that have come down through a family are often gifts bought in good faith. In such cases a look at the colour of the star, the lettering and the model name settles the matter of authenticity before any paid appraisal becomes necessary.