[GreenKeys] Teletype M12 KSR

[Jim Haynes]

I don't know about those dates.  Presume most of the orders for M12s
ended when the M15 went into production.  However Teletype had a
time-division multiplex line through the late 1930s, and they may have
used M12 printers for those.

Then after manufacture was discontinued there would still be spare parts
in production.  I think it's after WW-II that spare parts were 
discontinued, as it was late 1940s-early 1950s that hams had a fairly
easy time getting M12s.  The reason would have been that most of the
companies using them were ready to write them off when spare parts were
no longer available.

Something similar to the M26s - were made and adopted by the Bell System
in late 1930s, but were soon manufacture discontinued because they found
they could make machines cheaper by concentrating on just one model, the
M15.  And WW-II probably contributed to end of manufacture for the 26s,
since all Teletype production was going to the military.  Then in the 
early 1950s the Bell System decided to phase them out and allowed Teletype
to quit making maintenance parts.