Not necessarily. Montblanc regularly supplies its dealers with special packaging for promotional purposes. Years ago these were leather cases of their own; later they were complete sets of pen and tray. Such extras never appear in the regular catalogue and are therefore not to be found by searching the internet either, which readily raises the suspicion of a fake. That a leather tray of this sort carries only the name and no emblem is normal for promotional items. Anyone who bought from a long-established stationer can as a rule assume it is a genuine promotional extra.
The converse holds just as firmly, however: a flawless-looking box is no proof of authenticity, since packaging and paperwork are counterfeited and traded separately as well. What counts in any assessment is always the pen itself, supported by a completed service booklet and a receipt.