Bill,  The lock valve channel with the felt bushing on the Ampico A
typically goes about halfway into the upper body block, and then
turns (to the left in your picture) to join the main vertical channel
containing the intensity valve stem halfway between the upper and
lower seats.

The channel path is shown quite clearly in the 1923 Ampico A Service
manual.  I can send you a copy of the image if you don't have it or
can't locate it elsewhere.  If it is blocked with glue or leather
crumbs, it can usually be unblocked with small-gauge piano wire, which
can be coaxed to turn the corner of the channel if you know roughly
how it runs.

The small, roughly 1"x1" pneumatic mounted on the normal crescendo
pneumatic was common in late Ampico A instruments, probably starting
in 1927 or 1928.  The small pneumatic on each regulator was teed into
the line running the sustain pedal pneumatic, and they act as "sustain
pedal compensation", making the regulator play with slightly less
pressure (about 1/2" to 3/4" on gauge at the first intensity) when
the sustain pedal is actuated.

It is designed especially so that quiet notes play equally quiet with
the pedal on or off.  Without it, notes play slightly louder with the
sustain pedal on, because the striker pneumatics don't have to also
lift the dampers.  The same compensation function was part of the
Ampico B after 1929, but done with very different hardware.

Ralph Nielsen
http://www.historicpianos.com/