Hi All, The 'Rack & Pinion Tempo Control' has been positively
identified as being part of the ArtEcho system in a grand piano.
Here are a couple of scans from the Chart of Artecho Grand
reference.  Thanks to Ed Gaida for steering me in the right
direction (pun intended).

Musically,
John A Tuttle
Player-Care.com
Brick, New Jersey, USA

 [   Artecho grand drawer
 [ http://www.mmdigest.com/Attachments/18/01/17/180117_044825_ArtEcho-Grand-Drawer.jpg 

 [   ArtEcho Grand Tempo Control
 [ http://www.mmdigest.com/Attachments/18/01/17/180117_044825_ArtEcho-Grand-Tempo-Control.jpg