Instructions
Check the nib of the pen for inscriptions. The nib is the pen's writing tip. If there is an inscription describing the type of tip, such as "iridium point," it is a fake. If it states "Made in Paris" or any other city, it is also a fake. On a true Mont Blanc, the nib will be inscribed with a design and the number 4810.
Look for the serial number. All authentic Mont Blanc pens list the pen's serial number on the band of the clip on the pen's cap.
Peek under the clip. Authentic Mont Blancs will have an engraving of the word "Pix." You should be able to see it without needing to move the clip.
Inspect the box. The inside of a true Mont Blanc pen box set should have the signature Mont Blanc white star. This is generally on a plain black background. Counterfeiter boxes will often have the colors reversed with a black star on a white background. This can be a very useful strategy when purchasing Mont Blanc's through online auction sites.
Pay attention to seller feedback. Most of the fake Mont Blancs selling today are being sold on popular auction sites. Most of the amazing deals are fakes. To avoid purchasing one of these counterfeit pens, always read the feedback of other buyers. You'll be able to tell if the seller is in the habit of selling fakes. It is always safest to buy from a legitimate retailer.