Good one. I've worked on pinballs as a hobby (I have one of my own and am currently looking for another), and I am familiar with the plumb bob, the rolling ball, and the slam tilt.
I would point out that slam tilts are as common as dirt inside machines, and it is not unusual to find six or seven inside a machine: coin door, under playfield, both sidewalls, backbox, and so on. They are very simple mechanisms, and can be put anywhere there is room. And in spite of the fact that the interior of a pinball machine looks like Frankenstein's laboratory, there is always room for another slam tilt.