The location shown is Portsmouth Harbour, specifically the mudflats north-west of Fountain Lake and west of Whale Island, at high tide. The Admiralty Floating Dock AFD 5 (1912) can be seen to the right of the submarine's conning tower and Rudmore gas holder is on the left. This submarine is identified as U131 on a related drawing (PAF2084) but this must be wrong, since U131 was broken up incomplete in 1919-20 at Bremen. Technically possible alternatives might be U117 - U126, U139 - U141 and U160 - U167. Of these three groups, U139-U141 have the closest match to the bow shape but they had a second 5.9-inch gun abaft the conning tower and there is no indication of a projecting casing for it. There is also no obvious record of a U-boat being beached or stranded at Portsmouth in 1918-19 prior to being broken up, so this may be an imaginary composite rather than an on-the-spot study. See also PAF2084 and PAF2211.