[Boatanchors] What might this Johnson chassis have been?

[Ian Wilson]

Picked up a nice chassis today. On closer inspection it has a small "E.F
Johnson" label on the side; no other identifying marks.

There are 3 xtal sockets (no xtals). All the coils are octal plugins,
big M stamped in the top (Millen?), "74100" on top. There are some
bandswitching controls.

Tubes: 5Y3/VR150/VR90. Mixture of miniature and octal sockets.
Miniatures are 6AU6, 2x6BE6, among others. The octal sockets not in the
power supply sections are empty and don't have tube types scratched next
to them :)

There's some kind of small audio transformer on the chassis.

Was wondering whether it might have been some sort of SSB exciter? There
are no large coils anywhere (so there's no PA).

Thanks for any thoughts.

73, ian K3IMW