Definitely one for the "48 Hour" rule.
That being said, I have never used a typewriter in the early 1970s that had the "th" superscript in a smaller font similar to that seen in a couple of these memos. I did use Selectrics that could create a superscript by nudging the roller up and down, but it was in the same sized font. I don't remember if Selectrics or other advanced typewriters did proportional spacing.
As an aside, Microsoft Word will, unless otherwise instructed, change "111th" to "111th" automatically.
Some typewriter experts need to weigh in on this. I expect the blogosphere to take some time to digest it. I'd avoid conclusions for a while.