Happ Controls is a major manufacturer of parts for various sorts of amusement machines. To be more accurate, take the word "a" in that previous sentence and replace it with "the" and put it in italics.

If you see an arcade machine in the US, the button(s), joystick(s), coin door, coin validator, monitor(s), monitor bezel(s), light gun(s), trackball(s), etc are all very likely of Happ make, and even if it isn't made by them, they probably sold it to the manufacturer.

They are the company that makes the balls that go in pinball machines.

Their website can be found at http://www.happcontrols.com/