Hi, Ian. That "class" insignia was pretty unusual. There was a crossed-swords insignia from another class group and a small number more but most boats didn't have such an insignia. Many boats had a flotilla insignia ("Bull of Scapa Flow", the "Laughing Sawfish", the "Viking Ship"); also many carried an insignia of their "adopting towns" but these were usually one-offs. And there were individual insignia -- the boat commanded by Schnee had a snowman; the boat commanded by Swartzkopf had a silhouette, etc.
Later in the War, u-boat chiefs realized that Allied forces were using insignia to identify boats (e.g. if a destroyer reported that it had chased a u-boat with flowers for an insignia and another destroyer on the other side of the convoy had chased a boat with a teddy-bear insignia, then Allied Intelligence could assume that these were two different boats) and the use of insignia dropped dramatically.