The "Button Fastener: Attaches Buttons Instantly, as advertised on TV." Apparently, it "makes the perfect gift." Lucky for me, I still have the box! Do you think anyone would know this was a regift? ;)
The front view.
The back view.
A close-up, to see how the button fastener works.
Apparently, this baby was as seen on TV in 1972. It is essentially a tag gun, but as you guessed, it was used for attaching buttons. One recently sold on Etsy for $2.00. TEMPTING.
Anyway, call me up if you don't want to use that old pesky thread!