[GreenKeys] Black box

[Jim Haynes]

On Fri, 2 Aug 2019, W2HX wrote:
> common on typesetting equipment of that era (or perhaps later). I recall 
> Jack telling me this unit shared some similarities to the M26 teletype.

And Western Union made their 400-series printers using the same machine
converted to 5-level code and 5/16" gummed tape.  I don't know if they
converted leftover stock tickers or had some other source of the machines.