To add some more to Hal's "other pedal" theme:

My Crown Combinola has two extra pedals inside the normal two: one does
the mandolin rail and the other stops the hammers from reaching the
strings (just), and when used with the mandolin rail down it gives a
harpsichord-type effect.  Both of these pedals move sideways to lock
down, too.  This piano also has a hammer rail split into three sections.

The electric Recordo Gulbransen I had has 4 pedals too.  This time the
two extras are on the outside of the normal two, and these work a small
bellows set which allows you to pedal the stack while the motor runs
everything else.  This is like a "manual" setting if you don't want to
play the Recordo, and I never thought it was very successful.

Peter Coggins