The pen described is a Meisterstück 139, clearly recognisable by its size and the two silver cap rings. The missing '139' engraving is not unusual. The combination with a steel nib (instead of one marked 'G' for gold) and a long ink window points with high probability to a production between 1940 and 1943 — during the war steel nibs were used due to a gold shortage. The market value lies, depending on condition, between roughly 700 and 1,700 euros; well-preserved pieces can also be traded above that.