deckgun

As per the Navy Historical Center, this is the USS Rambler (SP-211): "Crewmen in action with the ship's forward 3"/50 gun, while she was serving in French waters during 1918. "Note that the image's inscription incorrectly identifies the ship as USS 'Rumpler'." See: www.history.navy.mil/photos/sh-usn/usnsh-r/sp211.htm

Catalogue of official A.E.F. photographs (1919): "41011. One of guns mounted on deck of German- U-boat 155. Caliber 5.9, length 20 feet. Marked Nr. 1412 L, Fried Krupp, 1917, 3984 Kg. London, England. December 4, 1918. " archive.org/stream/cu31924027944598/#page/n455/mode/2up "Deutschland was a blockade-breaking German merchant submarine used during World War I. It was developed with private funds and operated by the North German Lloyd Line. She was one of the first of seven U-151 class U-boats built and one of only two used as unarmed cargo submarines. After making two voyages as an unarmed merchantman, she was taken over by the German Imperial Navy on 19 February 1917 and converted into U-155, armed with six torpedo tubes and two deck guns." "U-155 returned to Germany from her final cruise on 12 November 1918 and was surrendered on 24 November 1918 with other submarines as part of the terms of the Armistice. She was taken to Britain and exhibited in London and elsewhere and was eventually sold for scrap in 1921. On 17 September 1921 she was being broken up at Robert Smith and Sons, Birkenhead, when an explosion ripped the ship apart, killing five apprentices" en.wikipedia.org/wiki/German_submarine_Deutschland#War_se...

As the merchant submarine Deutschland, U-155 visited the U.S. in 1916 and was the subject of other Bain photos, see:

en.wikipedia.org/wiki/German_submarine_Deutschland

en.wikipedia.org/wiki/French_cruiser_Amiral_Aube