[Aktungbby]

bmacauto! After a phone call to Frank at the USS Siversides Museum ( KISS principle in action BBY!): it is in fact a pass-through ammo hatch Further it is useful for cans of beer as well...(it wasn't called the 'cigarette deck' fer nuthin'!) We could not agree on what type of conning tower was present on the museum ship as the war: MOD I-IV produced several modifications often in-theater by a submarine tender often to the experienced skipper's preference. http://navsource.org/archives/08/pdf/0829294.pdf . Once the two 'ready ammo' water tight storage hatches on the conning tower aft fairwater each holding ten rounds were expended ammo would be passed up by hand from the gun ammo storage directly below the cigarette deck. (MOD IV connning tower?) The present deck gun is not the original. My source shows USS Gurnard with a similar hatch dated July 1945 so it is not a 'postwar addition'.