That makes sense. So, memo to what file, typed by what clerk? Where are the initials of the typist? Why does the memo show up in the man's papers, if they are part of an official file? If the non letterhead memos are CYA documents for his personal use to take home, why have them typed in such a manner, and expose these "office politics" and CYA antics to a clerk, when a written note would do?
Also keep in mind, this man has been dead for 20 years