I have a phone just like this that was from my grandfathers office desk. When I was a kid in the early 60's my father, who was an engineer built a contraption that allowed him to connect this to the phone system. We would call my grandmother every Saturday on it. He would click on the hook a few times and an operator would come on (a real person) and he would ask her to connect him to his mom's number. I remember doing those calls like it was yesterday.