In reference to Paul Morris question of sealing leather.  I recovered
our Ampico pump with kangaroo hide (leather) from PPCo using no sealer.
The leather is shiny black on the outside and greenish-yellow on the
unfinished side, glued with hot glue.  This was done in 1970.  The pump
is still in use and performing to factory specifications.

In addition I recall that someone once wrote about similar pumps used
to run those old pneumatic typing machines.  In their article they said
the pump arms would wear out before the leather showed signs of wear,
and the pumps ran eight hours a day for years.

Bruce Clark