Ten years after the ARC5 but I hope this rings a bell to someone.
I recently bought a small transceiver of what the previous owner claimed to be a radio from a US spy plane.
It is made out of two bare aluminum lunch box style units clamped together. The
top unit is the transceiver and the lower unit is the power supply. On the outside of the power unit is a 15 pin connector, 2 rows of pins for the external connections. no controls on the unit only a single BNC connector.
Total size is 24 x 21 centimeters and the transceiver uses mostly pencil tubes. Unfortunately 80% of the tubes is removed
The only marking is on the ID plate: in large print 5663 and in small print pt /no N650370-1 for the rest zero text on the in and out side.
Thanks,
Nico - PA3ESA