The M on a Montblanc nib stands for Montblanc and not for the nib width Medium; all Montblanc nibs bear this mark. The nib width is not stated on the nib itself or on the feed and can only be determined by inspecting the tipping or by a writing test. Nibs vary slightly even within the same classification due to handwork, which is particularly noticeable on EF nibs.