Following Steve Robbins' inquiry published in MMD 15.04.26, in which
he sought to identify a rotary pump, I emailed him privately showing
that identical pump as pictured on page 51 of the 1919 Ampico Service
Manual.

This service manual, which also includes "with 1920 Supplement,"
should be consulted to clarify any confusion.  The earlier pump "hides"
the amplifier inside the reservoir.  The 1920 Supplement describes the
more common, newer "external" amplifier as most people know it.

Early pumps had several features that are not seen in the more common
Ampico A pump.  The spill valve is operated by the amount that the
reservoir closes.  The amplifier devise within the reservoir can vary
the operation of the spill valve.  And the most significant feature
of this pump, is that the amplifier function is controlled by only the
treble stack pressures.  Again, the 1920 supplement explains the newer
amplifier which uses both bass and treble stack pressures to operate
the amplifier.

Mechanically, the pump has metal connecting rods and bearings that
look exactly like those found in Duo Art pumps.  That changed too in
the 1920 update.  Ampico pumps thereafter had wooden connecting rods
and felt bearings.

Steve's pump is found in early versions of the Ampico.

Bob Taylor
Missouri