Helicopter Sikorsky HR2S-1 Serial 56-004 Register 138421 used by US Marine Corps USMC. Built 1956. Aircraft history and location Aircraft History 138421 US Marine Corps 1956-06-22Sikorsky S-56, c/n 56-004, ff:? del US Marine Corps as HR2S-1, 138421, 22Jun56 soc & scr unk. 1957-01-10 soc 10jan57 Send Updates Use APP to upload photo @ (optional) When Now? / / Send