[GreenKeys] Teletype Code Diagram source?

[Sam Hallas]

I've had a request from an author to trace the source of Fig 5 at
<http://www.nadcomm.com/fiveunit/fiveunits.htm>

in order to clear it for reproduction in a paper he's having published. 
Sadly Alan Hobbs is no longer around to ask him where he got it.

It is titled 'Teletypwriter Code' and the RH column is headed 'American 
Teletype Commercial Keyboard'. My hunch is that it's either from a 
Teletype manual or from a text book like Telegraphy by Freebody.

Can anyone help?

Sam