An unambiguous determination of the nib width is practically impossible for laypersons and also difficult for experts, since the nibs are hand-ground and, e.g., a broad F can be very similar to a narrow M. An assessment based on photos is not feasible. With suspicion of a mix-up, the impression can be deceptive, because M nibs on the 144 appear too thin to many writers; a subsequently affixed nib-width sticker, however, that looks suspiciously over-stuck, can be a hint of manipulation by the seller.