Green Meisterstücks of celluloid stem from the 1930s and are rare, because coloured models were at that time less in demand and the green celluloid was less durable. Presumably it is a model 20 or 25; the exact model number stands usually on the back of the cap and can be determined from there. A small hole on the cap is structurally a ventilation hole and no defect. For spare parts and repairs of old Meisterstücks, Horst Schrage (max@maxpens.de) is a tried-and-tested point of contact.