It was first produced at the Mitsubishi-Urakami Ordnance Works division of Mitsubishi Heavy Industries. Later, the Imperial Japanese Navy established two manufacturing sites: Suzuka Naval Arsenal in Mie Prefecture; and Kawatana Naval Arsenal, a branch of Sasebo Naval Arsenal, in Nagasaki Prefecture. The Mitsubishi-Urakami Ordnance Works plant at Kawatana specialized in torpedo production and was destroyed by the atomic bomb dropped on Nagasaki. Technology transfer to Germany Germany approached Japan requesting the transfer of Japanese aerial torpedo technology. The Imperial Japanese Navy not only sent the plans, but also a number of Type91 aerial torpedoes to Germany in response. They arrived in Nazi hands on August2, 1942, courtesy of Japanese submarine I-30 as part of a yanagi mission. It was designated the Lufttorpedo LT 850 in German service. The weight of the LT 850 German version was somewhat lighter at , with a length. Germany wished to acquire the knowledge behind the Imperial Japanese Navy Air Service's aerial torpedo technology in order to more effectively attack the Allied transport ships steaming in the Mediterranean Sea. It had previously imported Italian-made aerial torpedoes, which became unavailable following the Italian Armistice of Cassibile with the Allies in September 1943. The indigenous German aerial torpedo designs were badly restricted in launch speed and launch altitude. Post-war commemoration Some 30 years after the war, surviving members of the development team raised money to privately publish a small book, Koku Gyorai Note or Aerial Torpedo Notebook. Type 91 torpedoes are currently displayed at the Etajima school of Japan Maritime Self-Defense (the Maritime Self Defense Force 1stTechnical School) and Shimofusa Base. They are missing the roll rudders. An excavated Type 91aerial torpedo is preserved at the Resource Museum in JGSDF Camp Naha, 1st Combined Brigade of The Western Army, JGSDF, located in Naha city, Okinawa. It retains the original features. It was picked up as unexploded ordnance by a bomb-disposal unit of the JGSDF. A captured Type91 aerial torpedo is displayed at the US Naval Academy, Annapolis, Maryland. It rests on two supports flanking a pathway in a small park in front of the Academy's Dahlgren Hall. Displayed on the other side of the pathway is a Type93 Japanese Long Lance ship-launched torpedo. References General references Privately printed book. Photographic print copies of Imperial Japanese Navy Action Reports. Prof. Ozawa is the designer of Ki-69. Seko was one of the last torpedo bombardiers of B6Ns. (August