The post by Craig Brougher yesterday reminded me that Seeburg, in one of
their early efforts, used a notched wooden rod to count coins with a
pneumatic that "subtracted" after each tune.  If memory serves, the
flat "rod" had two strips of copper or brass on it that made the
contact.  When the last tune played and the rod was moved, one of the
strips was shorter than the other and the contact was broken.

I am sure there are others out there that can give a better description
that I have.  Seeburg later went to an arrangement with pins in a
semi-circle with two pneumatics that moved the whole assembly from left
to right.

Ed Gaida
egaida@txdirect.net