Where case, lifetime guarantee certificate and pen do not belong to the same date, the explanation often lies in Montblanc's service practice of the 1960s and 1970s: when an expensive repair was due, the firm would offer the customer the chance to trade the old pen in against a current model, setting the estimated repair cost against the purchase price. Many customers took the offer up but kept the old box and the old papers. Hence the cases and guarantee certificates of, say, a Meisterstück 744 of the 1950s that still turn up today with a considerably later pen inside.
A typical case is the 1246P cartridge pen, built only between 1974 and 1977. In the old case with its rolled-gold papers it looks more valuable than it is, for it belongs to the ordinary everyday range rather than the top of the line.
In valuing such a set, then, what counts is always the pen itself and not the packaging. The original case and papers keep their appeal if the model that belongs with them can be tracked down later. Reliable figures are in any case possible only when the condition can be judged with the pen in hand.