“I am trying to find out what u boat my grandfather served on,all i have is basically one picture and what my mom has told me.I was told he was a machine operator/mechanic.He was based in Prussia and from the pic,i deduced he is an NCO at the time of picture,he also had a dagger with white ringed handle and an eagle pommel,also a white/light braid and pom pom hanging from the handle.Shoulder lapel is consistent with NCO rank no other marks on wool overcoat.His name was Walter Schwaericke .Also,he was Donitz private driver at some time,so i believe they may have served together before Donitz became admiral..Any help would be appreciated”