The meaning of the serial numbers is secret; therefore only Montblanc or an authorised specialist retailer can bindingly check the authenticity. Counterfeits also frequently bear serial numbers, so the mere existence of a number has no meaning. A positive indication is when the serial number is laser-engraved ("grey") and not stamped; certainty, however, is only brought by presentation to the specialist retailer. If the number begins with an "8" instead of with the letter "B", a counterfeit is to be assumed, since originals use corresponding letter prefixes.