This is one of UC-42's torpedo tubes. The photo shows the forward end of the tube - the section of the tube outside the submarine's pressure hull - the flange would have bolted onto the the pressure hull. The majority of the tube, (from flange aft), would have remained inside the pressure hull. The crew would have loaded the torpedo from the other end of this tube using block and tackle. (Photo courtesy Timmy Carey, Blackwater SAC, Fermoy)