[GreenKeys] Stunt box

[Rokumon Cat]

Hi again,
 
I have been wondering just what a "stunt box" is and how it is used. From what I have gathered, it is a mechanical device that is driven by the main motor in a 28, and responds to certain signals coming through the loop. 
 
I would love to know more about this, what it could do, how it was used, and if there are any left in the collector world. 
 
Thanks again!
 
Joe