These springs are jack springs.  When they were originally in the
pneumatics, there was most often a felt punching to prevent complete
closure of the pneumatic.  This served two purposes: (1) it prevented
the spring from flattening, and (2) it prevented the creasing of the
pneumatic cloth at the open end.

The felt punchings are the regulation punchings found on upright
action regulation buttons.  These were glued in before covering of the
pneumatics, but you may add them to the covered pneumatics with some
tweezers.

D.L. Bullock
www.pianoworld.us