Helicopter Sikorsky HRS-1 Serial 55-033 Register N2798 127799 used by US Marine Corps USMC. Built 1951. Aircraft history and location Aircraft History 127799 US Marine Corps 1951-06-02Sikorsky S-55 c/n 55-033, ff:? del USMC as HRS-1, 127799, 02Jun51 N2798 - ex 127799 Send Updates Use APP to upload photo @ (optional) When Now? / / Send