Helicopter Sikorsky HRS-1 Serial 55-019 Register 127785 used by US Marine Corps USMC. Built 1951. Aircraft history and location Aircraft History 127785 US Marine Corps 1951-04-02Sikorsky S-55 c/n 55-019, ff:? del USMC as HRS-1, 127785, 02Apr51 Send Updates Use APP to upload photo @ (optional) When Now? / / Send