Some Knabe grands had, I believe, Angelus players in them (pouch
type stack above the keyboard) with the multiple-scale tracker bars.
These would be early, maybe even pre-American Piano Company Knabes,
I suspect.

I had an Emerson grand with this set-up: a very, very fine piano,
but the keys were extremely long (like an added 10") to accommodate
the stack, and so it had a "clunky" feel during hand playing due to
the extra inertial mass needed to get the hammers moving.

Gordon Stelter