Jerry Organ showed a photo of a typical date stamp system card with the due dates stamped on it. And I have briefly described how that type of system typically worked.
No, he showed a single example of a library book slip (not a "card") with "date due" stamps. That doesn't make it "typical" or applicable to the Mosk memo.
So, did your embossed library card magically record the actual return date in some mysterious place (or what)?
Now you're just being silly. The library card itself wouldn't have that information. That doesn't mean that it wasn't kept. The purpose in bringing up the card was because you took your memory of a library card being
photographed with a page from the book and just decided that this was "typical", and therefore applicable to New Orleans. Unless somebody can prove that it wasn't. One anecdotal example is as good as any other.
No assumption, the evidence is convincing. The two words are synonymous in the context of this specific situation.
You find a lot of stuff convincing that you you just declare are "most likely" or "typical".
We have other evidence than just the memo. That is not "all we have."
Such as?