The stamp “Iridium Point Germany” is the single most reliable indicator of a fake. Montblanc has never marked its nibs in that way. The wording comes from mass-produced bought-in nibs and turns up on counterfeits of all sorts of brands; the country of origin, “Germany”, is every bit as invented as the rest of it.
Originals carry the word Montblanc and the gold content, that is 585 and 14 C or 750 and 18 K, and on the Meisterstück models the figure 4810 as well, a reference to the height of Mont Blanc in metres. Steel nibs from the cheaper ranges are stamped accordingly with the series or model name. A nib without any Montblanc marking at all but with a generic iridium legend rules out an original for practical purposes.
Counterfeits are especially numerous among the StarWalker models, while the large Meisterstück pens and the limited editions are also frequently copied. Since fakes are by now passable enough on the outside, it pays more to look at the nib, the feed and the quality of the engravings than at the overall shape.