Thank you! It’s called Taschenbuch der Kriegsflotte 1941/42. It was a book used on all warships and U-boats that summed up all the known ships from the main naval forces of both Allies and Axis. It contained detailed data about measurements , displacement, speed, armament, depth of keel, and silhouettes under various angles on bow. Captains used them to identify their targets and estimate speed, bearing, and other information required to come up with a torpedo solution.