As evidenced by the rectangular box with five knobs, the unusual player
mechanism in the Kimball piano is a type of Recordo system.
As Art Reblitz mentions in his book, "Player Piano Servicing &
Rebuilding," (paraphrasing) there were many companies that made player
pianos that could play Recordo rolls. Most of those companies designed
and built their own expression mechanism.
At Player-Care there are several references that cover a number of
Recordo systems. Over the years, I've found that having all of them at
my disposal makes the job of getting every system working correctly
John A. Tuttle
Brick, NJ, USA