[ Ref. Mark Buckland in 120623 MMDigest ]

Hello,  I had the same Symphonion.  After adjusting this mechanism,
it closes the coin slot in that moment when the main spring [energy]
is at its end, so that nobody throws in money when it can't play.

The trick is that the Geneva stop has a surface under an angle and
this surface makes a small arm move, but only when the Geneva stop is
in its end position and the main spring reaches its powerless end
position.  The angled surface is in the shape of a triangle which is
perpendicular to the rest of the (usual) Geneva stop.

When you wind up the main spring, the first motion of the Geneva stop
is enough so that the angled surface doesn't touch the arm anymore.
The small arm pushes a pin in the center axis of the main spring (when
the spring is at its end) and the pin makes a big arm move some degrees
so that its other end closes the coin slot.

Best regards,
Germar Schrimpf