I wrote most of this as a comment, and then decided I should post it so people won’t miss seeing it.
Here are some points about detecting forgeries. I spent roughly 25 years working on the problem of fakes, frauds, and forgeries for museums — but also on the problem of forged documents, sometimes for museums in connection with the history of objects, sometimes for the police, and sometimes for the court in cases of suspected forged wills. I then worked for a company in which, among other things, I was involved with — the manufacture and chemical analysis of inks and paper.
Keeping in mind that I have not seen the originals it would not be that hard to tell whether they were printed by a typewriter or by a printer. For openers, a typewriter strikes the paper, and modern printers spray the paper with various kinds of ink. One can tell the difference fairly easily by looking at the effect under a microscope; striking the paper will indent it at least somewhat. Striking the paper lays the ink down differently, too. Laser and jet printers spray the ink and it looks much more even than ink from any kind of typewriter — or from early computer printers that did strike the paper. Looking at what was shown on TV, the type looked to me like it was done on a typewriter, but one has to see the original to be sure. Also, the composition of the inks used are different for typewriters and for printers, and the ink should be tested.
As for things like proportional spacing, font choice, that small “th” etc. weren’t there electronic typewriters available that could do that? The 70s weren’t the dark ages. That wouldn’t be hard to pin down. Also, some of the Selectric fonts looked just like that.
If I were examining these documents, though, I’d look first at the chemical composition of the ink and the condition of the paper. Ink formulas change over the years, even for typewriters and printers. Paper ages quite a bit in 30 – 35 years, and there’s no reason to think any kind of special acid-free paper was used in Air Force Reserve offices for ordinary memos and letters. Also, the chemical composition of commercial paper coatings and fillers get changed by the manufacturers over the years. And these, too, age with time.
For a forger to successfully make an almost undetectable forgery of documents from the 70s would require (1) paper from the 70s, (2) ink from the 70s, which would not be easy to find in any sort of condition that could still be used because typewriter ribbons dry up and other inks settle out, and (3) equipment from the 70s. The equipment would be the easiest to get. I’ve got an old Selectric in the closet, and plenty of those balls in different fonts myself. It would take a really determined forger to locate all three, but of course that’s what they’re going to argue.
Beyond the physical attributes, determining whether these are forgeries would depend on comparing the wording of the documents with the rest of the correspondence of the assumed author to look for discrepancies in style and vocabulary. I don’t think there’s a chance in Hell that these documents were forged, but I’d have to examine them myself to be sure.