5.3 - 7 MHz ARC-5 transmitter.
AKA Command Set Transmitter
AKA SCR-274-N
AKA BC-458

Transmitter out of WW-II aircraft. Bombers used them. Yours looks to be in
reasonable unmodified condition.

Can be sold on e-Bay. If you do that, take photos of the back, sides,
inside top and inside bottom (many screws).

Colin K7FM