The SOC was the last of the “Curtiss biplanes in operational service” with the U.S. Navy and was designed for use as a scout aircraft for battleships and cruisers–capable of catapult operation and landing at sea. The Coast Guard acquired the final three produced by Curtiss in 1938 and these were designated as SOC-4s. They were assigned the Coast Guard call numbers V171, V172, and V173.
The Coast Guard acquired 13 total of four different variants of the famous Douglas Dolphin. They began acquiring Dolphins soon after the prototype model, named Sinbad, was introduced in 1930. It had an all-metal hull with room for 8 passengers and two flight crewmen.