"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.
Are there any other documents in Bush's file generated by this Killian guy?