I have come across these in at least four stacks that I have rebuilt in
the last 30 years, none of which was the model "B" Ampico.  The blocks
were teed into the port on the transmission frame that operates the
primary that activates the stack cut out in the pump.

I believe the information quoted at the end of D. L. Bullock's post
in 030405 MMDigest referred to the "B" Ampico.

Ed Gaida

 [ The manual, "The Ampico Service Manual 1929", simply calls the
 [ mechanism "The Ampico".  I don't know if the term "model B" was ever
 [ used in print by Ampico or by the successor Aeolian American Corp.
 [ -- Robbie