RCA "Prep Kit" Radio
While RCA was busy selling radios, TV's, phonographs, and records to the grownups, they hadn't forgotten the kids.  The RCA "Prep Kit" was an educational kit for the "junior technician", produced and marketed by the RCA Service Corporation in the mid 1950's.

The circuit is a simple grid-leak detector using a 1T4 tube and capable of driving only a pair of headphones from a strong local AM station.  The circuit was assembled on a piece of perforated Masonite, with a printed overlay to guide the young experimenter.  The only controls were tuning and a switch for the tube's filament.  No volume control was provided.  The radio was powered by a D-cell for the tube's filament, and a 45 volt battery.

There was a second circuit that could be built which added regeneration to the detector, for much improved sensitivity and volume.

Once assembled and working, the "chassis" could be installed in the corrugated cardboard "cabinet", which was the original package for the kit.