Leave it as Found. And I don’t know what you mean by “restore” but that is an excellent survivor. Anything you do that damages that Original paint would ruin the value. As it sets it is probably $1200-$1500. Of that were a five speed, you’d be looking at $3000+.
As odd as it sounds, the term comes from the flat solo polo seat, and yes it was invented for bicycle polo. In the early 1960s kids found these seats and began using them to customize their bicycles. That was not what these kids bikes were designed for but the name from the seats stuck.