This seems to be a class at a piano tuning or player technician school
(perhaps the Standard Action School). The teacher is pointing to an
action model. Above him is a Standard Action player stack. The model in
use by the teacher seems to show one upright piano note with it's player
mechanism. The bellows below it must operate the note. To the left we
can see another player model with various parts hung on the wall. Looks
like about 1918.

Philip Jamison
West Chester, PA