[mrob]

Not pure chance, because players could control how far to pull the plunger, and because players could nudge the machine. After the introduction of "tilt" mechanisms (eg: http://www.ipdb.org/machine.cgi?id=383 ) nudging became an accepted part of the game. It takes great skill to nudge effectively without triggering a tilt.

[losteverything]

How (& who) did one bet? Where were pinball machines located?

I was a King Kool master

[mrob]

This is the best article I found about the history of gambling with pinball:

http://www.pinballcollectorsresource.com/russ_files/gambling...