A small batch of color ImageWriter ribbons arrived, which were indeed still wrapped in their plastic, just as the auction had indicated. However, the plastic had holes in various places. So these were not after all the still-sealed ribbons I’d thought they’d be. I picked one and opened it, and it looked nice enough.
Then tried a print test. The ribbon worked I think, but the printer, not so much.
Now I think I may need to actually replace the print head, though I’ll need to do a little bit more research on what can cause this. This looks kind of familiar, in a vague sort of way. Maybe I just need to clean it? I’ll see.