Jeep,
I too recall the adds in QST and CQ from commercial companies
looking for 348's and ART-13's. I always figured that stuff was
destined for South America. Also, I knew an old timer that worked for
an exploration division of Magnolia Petroleum, and he worked with
BC-312's and 348's and even a Hallicrafters HT-9 transmitter. All of
this stuff was really considered obsolete in the early Sixties, but I
guess it proved reliable and was used for some form of field
communications.
I mentioned earlier that my father was a field engineer for Collins
from '52 to '55 and worked with the 18S and 180L tuner. I was a kid
back then 8 or 10 years old, and I still remember being intrigued with
the 18S receiver when he told me it had no B+ supply, but used 28 volts
for plate voltage.
John