Pop Out Quarter Window ?

They were not engineered to stay open. They were engineered for kids to pop open and spit their chewing gum out into the street; there were not yet seat-belt laws up here in 71, IIRC. Anyways kids were crawling all around in cars, and chewing gum was BIG in those years,lol.
'Course chewing gum was not the only thing being tossed, lol.