Pinging to Mindbender. This is up his alley.
You can make video look old very easily. In non-linear (computer) editing, you can add all sorts of effects. One is called “film look,” others add occasional dust, scratches, etc.
Easiest way to determine true age of video is to look at what you are seeing, especially the things away from the center of interest. If it looks like 1970s film, but there is a 2002 Yugo in the background, well, you get the idea.
Of course, any good editor can cover that kind of thing. Look for things like haircut styles (There is great film of J.C. Watts in the Orange Bowl taking about 45 seconds to stuff his ‘Fro into his helmet) women's fashions, men's tie widths, men's suit lapel widths, etc. Michelle is a snappy dresser. Her clothes and hair style will be a giveaway.
Also, how old does the principal look. If Obama looks 45 in the video, he probably was.
Early video tape (1980s field tape, not the stuff shot in a studio) can get a very pastel look, especially if edited down 3 or 4 generations.
1970s video shot in a studio such as a news show will not disolve or cut to a video tape. They did not have frame lock and if they didn't go to black before and after the tape, the picture would roll.
Look for style. Early news reports had very long individual sound bites, very “officialezze,” as much as 30 and 45 seconds per bite. They have become shorter every year. Also, if it's really film, the fidelity will be bad.
Look for mic flags. Networks and individual stations often change the styles. If I can see a mic flag (those attachments on a microphone that tell you whose mike it is, who the reporter works for) I can probably date the video within 3 to 4 years.
Wireless handheld mics? New.
If he is speaking in a prepared speech in front of 10 or 15 assembled microphones, it is probably old. Now they use one or two mics and a “mult (multiple output) box.”
The real trick is to watch it ten or fifteen times. You will begin to see things you never saw the first time.
Good luck and send me any links and I'll give it my best guess.