This was given to me by a friend today, who had visited a recent Mardi Gras parade. His girlfriend found it while randomly scavenging around.
It originally had a red rubber band on it, but that ended up cut and lost, hence the regular rubber band to keep it closed. Thankfully it was never used though.
Here's a folding crossbow from the 1930s.
https://share.google/kkAVf3d3f3zo4Q0x7
I don't feel like searching, but I'm pretty sure there are examples going back to ancient China. Just because your dad submitted a patent for something doesn't mean he invented it.