I grew up in a family with two grand pianos, one Settergren baby grand
and one Steinway B.  The Settergren had the usual duet bench, but it
had two brass flip-out braces on the sides to convert it for player
pumping.  I never knew what they were for until getting interested in
mechanical music much later.  No idea why it was with this straight
piano.

A somewhat nasty friend who had an unrestored upright would demonstrate
his ability to pump his old leaky player, and challenge anyone to do
as well.  The new person would sit down on the stool, which had been
covertly restored to flat-top status, and try his luck.  Most wound up
falling over backwards until shown the trick of lifting the seat to
install the shim properly.

Jim Katz