Assembly details, fairly apparent.
Each unit is self powered, the large bodied grounded plug assembly just fits through this hole necessitating a keyway for other cord.
Another peek at woodwork, only one side is drilled like this..
..which makes for a nice view.
Though to be fair, the ample ventilation provides for largely unrestricted observation.
I found service data! TIC was evidently acquired by Acton Labs in the mid 1950s (or thereabouts), and in reading this thread it would seem TIC was H.H. Scott's company after departing GenRad? http://antiqueradios.com/forums/viewtopic.php?f=8&t=221316
Regardless, I'm happy to have a roadmap I can follow should I decide to tackle the motorboating issues. I'm somewhat on the fence about that, because of an interactive response to signal that nudges these into musical instrument territory.