[ARC5] Scarce ATA Available

[David Stinson]

This is one of the early 1944 runs of ATA 2.1-3.0 transmitters
that were built by A.R.C. on the ARC-5-style chassis.
Note the tuning window has screws, not snap slides.

http://cgi.ebay.com/150552342371

I've see about half a dozen of these- they come up every couple
of years or so.  Often enough for me to rate them as "Scarce" 
rather than "Rare."   All were in "NOS" condition, 
so I wonder if whatever they were produced for didn't happen.
I used to think they were produced as replacements, 
but now I'm not so sure.   Never seen any documentation, 
so all we're likely to ever get is "informed speculation."
There were a lot of  allies coming into the fight
by 1944, and they were getting equipped by Uncle 
with things like SCR-274N.   
The South Americans got a lot of SCR-287.   
These-....  hmmm.... what word to use?
I don't want to belittle the efforts of someone like Brazil
by calling them "secondary" or the like; everyone's efforts
count in such a task and should be acknowledged.
Anyway- most of their navies were still on the "1920s"
frequency agreements, using long- and medium-wave 
for just about everything, including aircraft.
I wonder- would the idea of these sets have been
to add a 2-3 MC componant to SCR-274N?
It certainly would have made sense at the time.
No way to know for sure, of course,
but it does fit the known facts.
Any other "informed speculation?"

73 Dave S. AB5S