I operated an IBM MT/ST (Magnetic Tape / Selectric Type) for the Army in 1972/73. It could have had the heading centered on the recorded "template" that was used for such. (I cut orders using a library of pre-recorded "boiler plate" or standard format.)
However, that setup was VERY EXPENSIVE and could never have produced the proportional space, superscript, kearning etc. The forgery is, indeed, obvious.
But Selectric typewriters were not proportional font, only the Executive models were. I hadn't ever heard of this Selective variant, but I can guess that you would re-wind the tape, and play it back so the typewriter would duplicate the form.
In order to fill out forms, they need to be "aligned" with the text, so that you can fill out the little boxes. Proportional type isn't aligned. Every letter has a different "space" it lives in.
Now just imagine a LtCol using any such typewriter just to make notes for his personal file.
Nope. Ain't going to happen.
Almost no one has commented on the raw improbability that:
1) the LtCol would create typewritten memos to himself and sign them, just for his personal file.
2) That they would show up somewhere, anywhere, 30 some years later after he was long dead.
If the guy was just looking for some CYA, he could far easier just keep a written notebook. Much easier to carry around.