This is not a complete answer, because I haven't identified the video directly, but it has some information which I think should help someone interested in finding it.
I am now pretty sure (despite my original answer in the photography SE) that this is footage from one of the Apollo TV cameras. The 16mm film footage is simply higher quality than this is.
When was it taken?
There are two parts to this question:
- which flight was it taken on?
- in which phase of the flight was it taken?
I don't have an answer to the first part, except I think it probably is not Apollo 11, as I've looked through all the TV from that and there's only one candidate which I think it's not in fact. But it is possible to say something quite detailed about the second part, which should help prune any search for the answer to the first part.
So, when in a flight was it taken? Well, to answer that you need to know that the Apollo flights landed on the Moon during the lunar morning. For instance Apollo 11 landed on the 20th of July 1969 which was 5 days after the new Moon.
Well, this tells us what the phase of the Earth was as seen by the spacecraft once they had left Earth orbit, and how it changed over the flight. Note: I am assuming that this was not taken from Earth orbit: it would be bizarre if it was I think, as it would need to have been with a very wide lens, and probably the edge of the window would have been in the frame.
And the answer to this is that they were looking at evening on Earth (so in this footage north is up), and that as the flight went on the Earth waned: the illuminated part got smaller. This is pretty obvious if you think about the geometry a bit.
Well, I then had a look through the Apollo 11 flight journal, and it's very clear from that that the Earth has not waned enough on the outward flight, or I think while they were in lunar orbit. There is a candidate from day 8, towards the very end of the TV transmission that day, but I am not sure that this is right: note that the Earth is 'upside down' in the footage: north is down, so we'd have to assume that whoever took it for the Eno footage knew that and turned it around; I am also just not sure the weather patterns are the same.
How to search for it
I think that the information that the Earth was waning gives someone with enough time on their hands enough information to find the footage:
- you're looking for a flight during which the Earth was about half full;
- this means that the Moon was half full as seen from the Earth;
- so you can use information about the phase of the Moon during the flights to work out which flights are candidates (but see below);
- start at the Apollo flight journal home page;
- then, for each candidate flight look for TV footage, and can it to look for the Earth in it – if it is fuller than the Eno footage skip to the next chunk of TV (or so some cleverer bisection search than this).
A caveat: the Earth-Moon trajectories were obviously not straight lines. Particularly when they were close to the Earth they were looking at it from an angle quite far from the Earth-Moon line, which means the phase of the Earth may be significantly different. I think this means it was fuller than you would expect at the start of the flights and less full than you would expect towards the end, but I'd need to think harder about this than I have.
Another problem: a lot of the Apollo journal entries don't have the TV footage in them. This will make it harder to find unfortunately. I'd just looked at the Apollo 11 entries when writing the rest of this, which do have the footage in them. Sorry!