Update on this thing. As I mentioned, this came from my dad's stuff, which came to me when he died. I couldn't figure out why he had this thing as he was not one to keep things around that he had no use for. On the other hand, he loved to 'repurpose' things and liked it even better when you had to ask him what a thing was used for.
I never got to ask him about this thing, so I asked my mom about it.
She said he had it rigged up for use as a slingshot. Go figure.