I'm on agreement with Homebrood on this. I would never add a doorbell to one of my add a ball games. I would rig a coin return button switch as mentioned. However I have a couple of games where this was done prior to purchase. It seemed to be pretty common. Both of the games have doorbell buttons that look older than the game itself. One is art deco looking and looks like it was made in the 1940's.

I'm leaving them. Maybe if I was doing a full cabinet repaint, I would remove it and fill the hole, But as is just adds to the nostalgia.