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. The first example was purchased for $31,500 in 1931 and was designated as RD for a transport built by Douglas. It was delivered on 19 March 1931. It was not an amphibian but utilized beaching gear. The Coast Guard christened it Procyon and assigned it to Air Station Cape May, New Jersey. The Coast Guard soon after acquired two other Douglas RDs that were somewhat different in that they were true amphibians. and were equipped with more powerful Wright engines. They were designated as RD-2 and delivered in1932. The service acquired ten upgraded Dolphins in November, 1935, and these were officially designated as RD-4s. The Dolphins were numbered and also named for stars. The last RD-4 was retired in 1942.
