[GreenKeys] Was there a keyboard for a 20 ?

[Jim Haynes]

Yes, they have been sighted.

I originally didn't believe there was any such thing, because the Model 20
is used for Teletypesetter service and that is always done with punched
paper tape using an elaborate keyboard perforator that can deal with
proportional spaced type.  But Model 20 keyboards have been sighted. 
Maybe someone in the Bell System believed there was a market for a system
that could transmit up/low case by wire.  (Which was also the purpose of 
the IBM 2740 many years later.)