I found a tour of the Hallicrafter's plant on line.
This is a WW-2 propaganda film, dated 1944 and titled "Voice
of Victory". In two parts at http://www.archive.org
It has considerable detail on the construction of the
BC-610 and shows some other products in somewhat less
detail.
--
Richard Knoppow
Los Angeles
WB6KBL
My bet is they didn't need always need a heater in the back of the SCR266.
Interesting to see all the dollies and come-alongs used in production.
Also tons of other neat-o screen gems at that site. A keeper.