Engraving is handled through the authorised specialist trade and the boutiques. An engraving in one of the standard typefaces on offer can often be carried out on the spot; if handwriting is to be reproduced, however, the pen has to be sent in to Montblanc, which takes correspondingly longer. When a new pen is bought, the dealer will often include the engraving free of charge as a voucher; otherwise it is charged for.
For pens not bought new from the dealer in question, proof of provenance is sometimes asked for, such as a stamped receipt or a completed service booklet. Practice is not uniform, which is why it is worth asking at the boutique or at one's usual dealer; in principle any specialist dealer can arrange an engraving. Bear in mind that an engraving cannot be undone: a personal dedication as a rule reduces the resale value noticeably, whereas an old engraving in period style on a pre-war piece counts as part of its history and is less of a drawback.