I'm sure you know how you'd have to center manually with a purportional typewriter. Type out the header, figure out exactly how many fractions of a space you'd need, skip over exactly that amount. It wouldn't be pretty.
NO ONE, would do such a thing by hand.
It might have been possible with a "memory" typewriter in the 80's. But I don't think any such thing existed then. I don't even think they had calculators in early '72. If so, then they were very rare and expensive.
The first "memory" typewriter that I remember seeing was a hugemungous gollywog IBM Daisy-wheel gizmo that had what looked like a television tuner on the right side of the keyboard -- that was about 1983, if I recall correctly.
It's appearance was quickly forgotten as it arrived simultaneously with the first "personal" computer I had seen in a military office. I forget what brand it was, but the operating system was CPM. It also used a standard daisy wheel printer.
Everywhere else in the military between 1976 when I enlisted and 1988 when I was discharged, the normal office workhorse typewriter was one of the IBM series using typeballs. Producing something like the target "memos" on one of those suckers would have been impossible.
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.