Google comes up with vintage drapery hanger hooks:

Vintage-Brass-Curtain-Drapery-Hanger-w-Safety-Pin-

To hang up infants by their diapers, just kidding.

mdln, childcare in the 1930s was brutal.

olychick, thank you! I should learn how to do an image search myself. And hey, they go for a nice price on Etsy!

My next question is, how do I find a picture of them in use?

bpath, just so you'll know, I didn't do an image search but used words. I think I used "vintage large safety pin with hook" and found those. I don't have enough experience hanging draperies to offer a credible clue as to how they worked, but maybe they were pinned on the back of pinch pleated draperies and the hooks went through those holes on a traverse rod?

I’ve never seen anything like that before. Interesting.