The white emblem on the cap top is not a star in the strict sense, but the stylised, snow-covered summit of Mont Blanc with its six valleys. The shape and the number of the points are thereby fixed: an emblem that looks angular, or one with only five edges, points to a fake.
Some of the counterfeits are conspicuous simply because the emblem is executed not in white but in black. On particularly high-quality writing instruments, such as some Limited and Special Editions, the emblem is made of mother-of-pearl. As the differences are fine and are barely apparent in overview photographs, it is worth requesting a sharp close-up of the cap top before making a purchase at a distance.