" The use of proportionally spaced fonts did not come into common use for office memos until the introduction of laser printers, word processing software, and personal computers."
Not to throw a monkey wrench into this, the IBM Executive typewriter did have proportional fonts. I used one in the army in 1975-78. It was probably a few years old, as it would have been a hand me down from S-1. Most small letters would have been a full space. The letter "i", a puctuation mark, etc. would have been a half space.
If I remember correctly, and "M" or a "W" was two full spaces, or at least a space and a half.
The type on the memos looks familiar to me. I think that I would find a way to compare it to an IBM Selectric before drawing any conclusions.
Blessings, Bobo
Could your typewriter type superscripts?
It would be nice to see the paper. Not only is the font proportional, it looks like there's some kerning going on. In the word 'failure', it looks like the top of the f overhangs the a. That required a typesetter in the 70s.
Unfortunately, I suppose that 16 generations of photocopying could mimic this. But, why in the world is somebody's private copy get photocopied 16 times?