How should one react if a historical Montblanc 324 from the 1930s has been lost during a repair by Montblanc, and how can the value be realistically estimated?

In value determination one must distinguish between asking prices and actually achieved sales prices; real sales prices of a 324 with gold nib often lie around 90 euros, for coloured or rare variants higher. The assumption that an 18C gold nib alone is worth 150 euros is unrealistic; the material value lies clearly below. As orientation, the guide on value determination written by the collector Axel ('penparadise') is recommended, which most collectors in the forum follow. The collector should negotiate soberly with Montblanc and not make excessive demands but justify the realistic market value with comparable concluded auctions.