I am restoring a 1915 Weber upright Duo-Art.  It was built before
they added the auto rewind and replay bellows.  This is the second
restoration, the first having been done in the 1970s, I believe.
Much of the small diameter control tubing had broken and fallen into
the bottom and we could not identify all the connections.

There are two 9/64-inch nipples on the bass side at the back of the
expression box.  One probably connected to a valve on the hammer rail
lift (soft pedal) pneumatic, which opens when the pneumatic is
collapsed.

I cannot find a connection for the second nipple.  They do not appear
on any of the tubing diagrams I have consulted, of course.  Does anyone
know what is their purpose and where they connect?

Thanks,
Joseph Osborne
Carlisle, Pennsylvania, USA