Collectors report that the model designation on the Montblanc 252 (small variant of the 25x series from the 1950s) is on the turning knob, while the cap ring then remains blank and only the Montblanc inscription stands on the cap. The models can be classified in time on the basis of engraving position (cap ring or turning knob) and ink-view window (blue or white); for this, the Montblanc Diary by Wallrafen/Rösler is a recommended reference. The value depends strongly on supply, demand and above all condition and cannot be flat-rate quantified. Serious research in the specialist literature obviates many direct value questions.