Question about a helicopter

[Sgt_Tropo]

I think Andy has the timeline just about nailed. It looks as if there might be a minigun covered by the tarp, just outboard of the rocket pod. This was indeed the early mounting system for the mini's. Also, the earkly gunships didn't have door gunner M60 mounts because the early birds didn't have the new and improved main rotors for the additional lift / payload capability. herefore the early gunships used only two man crews to save on weight. With nobody in the "cargo" bay, there was no need for a door-gunner.
These early versions of the gunship used a greese pencil mark on the windscreen as a sight for the co-pilot. It was really amazing that these guys were as good as they were in putting the fire power in the right places, especially when in close !
I believe the new rotors became available and began wide deployment in RVN sometime in early to mid 1968. The new high-lift capable rotors allowed the Hueys to (1) carry more men into battle, (2) allowed the gunships to carry both more armament (fire power) and door-gunners and also allowed the dust-offs to be able to carry up to eight litters and two or three corpsmen. The previous models only allowed for 4 litters and one corpsman.