On electromechanical pinball machines, sound is provided by the chime unit. There's typically also a tone box that amplifies and enriches the sound produced by the chimes.

I couldn't find a model for a Gottlieb tone box specifically, so I decided to model mine for posterity. This was modeled from a 1977 Jacks Open.

Printing notes:

Use 2 perimeters, to make sure there's enough anchoring area for the large bridged top surface. Designed for 0.2mm layer height.

In PrusaSlicer, I had to disable “Detect bridging perimeters”, and set a custom bridging angle of 180 degrees for the bridging to slice properly. See the included slicer screenshot.

The screw holes have an 0.8mm wall closing them off, to make sure the acoustics stay good on unused holes. You can either drill this out or simply put the screw in, and it will punch through the wall.