I'm just a little curious as to how many of these mechanism's where
made, and how rare they are today.  Are there many around still?

I know of one such instrument and it intrigues me with those second lot
of holes on the tracker bar. I understand how they work but have never
seen a roll for one let alone heard one play, (the one I know of doesn't go)
although it is all intact, including the row of pneumatics for the hammers.

I'm not that excited about the "Cable" piano it's in as has a very
ordinary sound (as all other Cables I have heard).

My big question is: "Are these worth  hanging onto or not" ?

      And whats the chance of finding some rolls for one ?

Michael