No. 87 Squadron, including Arthur Vigers, experimentally fitted some aircraft with two forward firing, unsynchronized Lewis guns mounted on top of the lower wing, just inboard of the inner wing struts. These guns could fire incendiary ammunition, which could not be used with the synchronized Vickers guns. The 97-round ammunition drums could not be changed once empty, nor could the pilot clear gun jams, and the field modification did not become standard. Postwar service Dolphins were quickly retired after the war. Nos. 19 and 87 Squadrons demobilized in February 1919, followed by No. 23 Squadron in March. The last RAF unit to operate Dolphins was No. 79 Squadron, based in Bickendorf, Germany, as part of the British Army of the Rhine. No. 79 Squadron demobilized in July 1919. The Dolphin was declared obsolete on 1 September 1921. No. 1 (Fighter) Squadron, which operated Dolphins along with S.E.5as, Sopwith Snipes, and captured Fokker D.VIIs, was disbanded on 28 January 1920. Although retired from Canadian Air Force service, a small number of Dolphins were sent back to Canada. One Dolphin was converted for civilian use. In 1920, Handley Page obtained serial no. D5369 and operated it as a demonstrator under the civil registration G-EATC. This aircraft was sold in 1923. The Polish Air Force operated 10 Dolphins during the Polish-Soviet War. From August 1920, these aircraft were primarily used for ground attack duties in the Battle of Warsaw and other actions. They were soon grounded due to lack of spare parts. In October 1920, two Polish Dolphins were loaned to the Ukrainian Air Force (1. Zaporoska Eskadra Ukraińska) for use against the Soviets. Both aircraft were returned to the Poles in February 1921. Production and planned developments A total of 2,072 Dolphin Mk I aircraft were produced by Sopwith, Darracq Motor Engineering Company and Hooper & Co. Approximately 1,500 Dolphins were stored awaiting engines at the time of the Armistice. These incomplete airframes were eventually scrapped. Two developments of the Dolphin were planned. The French firm SACA (Société Anonyme des Constructions Aéronautiques) commenced licensed production of the Dolphin Mk II in 1918. The RAF expressed no interest in this variant, which was intended for the French Aéronautique Militaire and the US Army Air Service. The Mk II’s 300 hp direct-drive Hispano-Suiza 8F gave a maximum speed of and a ceiling of . The new engine had a displacement of 18.5 litres (1,129