[GreenKeys] Versions of the Model 28 keyboard...

[Randy or Sherry Guttery]

I'm trying to figure something out... and just about the time I think I 
have a handle on it - I get some new information that just muddies 
things back up.

The question is this: how many keyboard "generations" were there? When 
did each hit the street? Are there any easy / fast ways to identify each 
generation.

Here is my "take" so far:
There are four- with pretty clear distinctions between the last two - 
while the first two seemed to be less a "new model" as a progression of 
improvements that "finally" started being named.

Specifically: The first keyboard I'm calling the "Pre MKI" as I have not 
found it "named" anywhere. This is the first keyboard issued - and has a 
few characteristics that (so far) make it fairly easy to identify.

Then there are the MKI through MKIII.  The II and III are pretty well 
documented - as Teletype better identifies them in the documentation. 
Often they identify the "current" (for that issue of manual) keyboard - 
then also note "earlier design parts" or such. I have seen such 
references in say a manual where the "primary" keyboard is a MKII; there 
is a reference to "earlier parts / design" (Which implies MKI) - BUT 
those parts (the earlier ones) are nothing like what's in my keyboard.

We know that my keyboard (and the original typer) all date from late 
1950 to early 1951; and I have a Navy manual from December 7, 1950 which 
matches exactly.

Here are some things that seem to set what I'm calling the Pre-MKI apart 
from all later keyboards:

1) the repeat key is in the center of the keyboard (slot #21). It 
operates through a vertical "slide" on the generator frame - which then 
pushes an extension on the code bar reset bail latch to keep the latch 
from latching - and allowing the generator to run on. None of the later 
keyboards I can find documentation on (from 1953 - which I *think* is 
when the MKI hit the streets) have this sort of repeat arrangement - all 
the later ones have a key/keylever down near the right end (slot #37) - 
and operate through an extension on the non-repeat bell crank lever (the 
extension does not exist on the earliest keyboard). The later ones do 
not have the "back" extension on the code bar reset bail latch - since 
that's now "handled" by the non-repeat lever / bell crank.

2) the earliest keyboards have holes in the top row for the six 
installed keys (Lock, Unlock, Break, Loc CR, Loc LF & repeat). The newer 
keyboards have all 42 holes drilled - and unused / spares "plugged" by a 
filler cap that is held by a tinnerman type nut.

3) the code lever universal bail in the earliest keyboards does not have 
an adjustable "extension" that holds off the non-repeat lever.  The 
newer ones are adjustable - by loosening two screws.

4) the adjustment to set the ball "gap" in the ball track is a metal 
lever that is held in place by a screw. In the newer keyboards - the a 
screw contacts the balls directly and sets the gap.

5) the non-repeat assembly plate mounts on the earliest keyboards with 4 
screws - while the newer keyboards use only 3.

There are many other subtle differences - the problem (project?) is 
trying to identify which is what generation... Again - it's really muddy 
between the "pre" and MKIs.

Are the "Pre MKIs" really MKIs that just went through some serious 
changes before Teletype finally changed the designation? Esp. since they 
probably didn't "think" about changes very early on...

Here's another "point" in my four generation theory:

The Navy lists the generations of the keyboard as
MX-1114   used in TT-47 and variants (gov, table top, etc.)
MX-1114A  used in TT-47A and variants
MX-1114B  used in TT-47B TT-47C and variants
MX-1114C  used with TT-47D and variants...

I'd like to just go down these and make the pre-MKI through MKIII - but 
that's guessing - and unfortunately all the Navy says is "same as above 
but improved").

Of course the typer went through some serious changes as well... there 
are at least three serious versions of it as well... These are 
documented by the Navy as
MX-1115   used in TT-47 and variants (has that sliding range adj.)
MX-1115A  used in TT-47A and variants (has the familiar knob adj.)
MX-1115B  used in everything after the "A"s...

Thanks for thoughts, suggestions, etc.
best regards...
-- 
randy guttery

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