It was first introduced in the late 1950s.
OK......Someone needs to research whether the specific font used in these memos existed on the IBM at the time.
Who can do this?
It likely did. The Executive Selectric had an interchangeable ball, rather than hammers, that struck the paper. These balls representented the different fonts.
Some offices had ten or twelve different balls.
The easiest way I would suppose would be for some older soldiers here to compare there paperwork from the period and see if the type matches, may not be a perfect way but it is a way.
"OK......Someone needs to research whether the specific font used in these memos existed on the IBM at the time.
Who can do this?"
Tough to do. I've looked everywhere on the web, and cannot find a single example of a document typed on an IBM Executive. Nor can I find any font examples for that machine.
There are precious few of these in working order now. Perhaps a typewriter collector would have one.
I believe with the IBM Selectric, the balls used could be any font. Replace the Selectric ball, replace the font. I used to have to do this to type letters in Spanish and French.
In looking at the font, it doesn't seem to be one that I wouldn't have used back then. Sorry but very few items were actually monospace with the Selectric. An old-style typewriter would be a different story.