It's an irrelevant nit-pick, FWIW. Everybody on this thread agrees the documents were not made on that model of typewriter, but not for exactly the reason you gave.
The IBM Executive does proportional type, and could be fitted with special strikers to make the "superscript st." But several paragraphs of text, in the closest of the available fonts, would not match with the precision shown by MS word (yours) vs. the forgery. Therefore, the forgery was produced by MS Word.
See my reply to MineralMan. MS Word does different spacing in the same example of "iiiii", "ooooo", "wwwww", "mmmmm".
It's probably that nasty Kerning that does it. The IBM didn't have it. MS Word does.