Which model and which value are an inherited antique Montblanc fountain pen from family possession?

It is a Meisterstück from the 1930s, based on the indications given presumably a 25. The exact model number is embossed at the rear on the turning knob of the filling mechanism. It is a push-knob filler with an ink sac inside; after long non-use, the sac typically has to be renewed, for which specialised restorers like Horst Schrage (max@maxpens.de) offer themselves. For value determination, the relevant collector guides and a comparison with current eBay auctions are recommended; 25s are not rare, so patience in market observation is sensible.