Brake Drum Hub Assembly Mystery

new rear drums were held in place with a push nut (like what hold hood hinges to the body) at the factory so that the whole rear axle assembly could be moved around and installed without the drums falling off. Several years ago I bought a 73 Dart with 27,000 miles on it and there were two pushnuts holding each rear drum. 40 years and the drums had never been off the car...