Be careful with this. The IBM Executive typewriter used proportional fonts, and was a staple in the military. It was first introduced in the late 1950s.
"Could it do superscripts with reduced font size like in memos 1 and 4?"
Yup, it could. A superscript "th" and "st" were available. They were treated as a single character and were one of the characters above the numbers. It was an option. IBM sold Executive typewriters with a whole range of special characters, for foreign languages, mathematics, etc. You wouldn't believe.