Its sender, Alan Brignull, assured me that he didn't mind being identified here. So thank you, Alan, for your package, and I hope my return package has reached you by now. Alan is a printer whose wonderful letterpress work you can see by searching Google Images for "Adanaland."
In addition to sending me an interesting '60s article on typewriter typefaces, including proportional ones, Alan contributed this thought-provoking reflection:
What do typospherians think? Does this count as a typecast? What is a typecast anyway, and what is its purpose? I'll follow up with some thoughts of my own in a few days. (They can now be found here.)