c5a

We see drums in the cargo hold. I know very little about aviation but it always impressed me that C-5s had drums of military specification hydraulic fluid in the cargo hold. They had to top off the hydraulic systems because of leaks. When I asked a (rightly-proud) C-5 crew member about the drums, he asked what I would expect from an airframe with miles of hydraulic lines.

Outstanding

A bit of photo manip shows it's C-5A 66-8306 MAC

There isn't quite enough detail in this photo to nail it down for certain, but this is plausibly (perhaps even probably) a photo from the first flight of the first C-5A, June 30 1968. Only two C-5As ever flew with the instrument nose boom, airframes 0001 (AF66-8303) and 0002 (AF66-8304). There was only one nose boom, and it was used on 0001 from June 30 1968 until the airplane was accidentally destroyed in a flight line fire on October 16, 1970. After that date, the nose boom was transferred to 0002 to complete flight testing. Although this could be either one of those airplanes, also noteworthy is that there is a Lockheed T-33 in the image. There was a T-33 used as a chase plane on the June 30 1968 first flight of airplane 0001. It's not possible to read at the level of resolution in this scanned image, but the original may have enough detail to reveal the identifying numbers. The USAF serial number is of course on the tail, the Lockheed airframe number is dimly visible (but not legible) as a dark smudge just aft of the radome in the grey area of the fuselage. (Nose boom trivia: after C-5A flight testing, the boom was stored for a few decade. It was pulled out for use again on the first C-5M in 2006. The nose boom was -not- used during C-5B flight test.)