This is the Futaba R603FF 2.4GHz FASST 3-Channel Receiver.
used in the 2.4GHz 3PM Pistol Grip Radio.
Futaba R603FF 2.4GHz FASST 3-Channel Receiver
Reception Antenna: External
Power Requirement: 6V NiCd battery
Size: 1.5 x 1 x .55" (39 x 26 x 14mm)
Weight .45oz (12.8g)
Futaba 3PM Computer Radio with the 2.4GHz FASST System