[R-390] I was unaware they made this cover(pics)!

[Flowertime01 at wmconnect.com]

Glen,

No need to guess. You are right.
These could be "black out" covers. The R-390A does not have a dial light 
dimmer. When the radio is used in a shelter, at night, there would be a 
requirement for a black-out door or turning off/covering up all light 
producers for someone to enter or leave the shelter. Glenn WB4UIV

Our field stuff in Nam had them in 69. We hated the things because 
they do not stay up and you have to hold the cover up when you went to dial 
onto a 
frequency. The Vans in Korea on the DMZ had them in 70 - 71. Those were
relegated to the motor pool and were just a maintenance problem to keep the
stuff "hot in the depot" [parked, but not yet junked] operating.

We had a couple on some receivers in the field station at Torri Station 
Okinawa.
Those receivers were monitoring some propagation beacons on some fixed 
frequencies. You could walk by the chart recorder, see where the needle on the
recorder was as you went to work and knew if you were going to hear any thing.
It was easy to just keep the dial covered. 90% of the station ops and 
maintenance
folks did not even know there was a special project running over in the 
corner.
We were just collecting data. 

Mostly they were like the micro dials on the BFO. Sort of official after 
market
bolt on accessories. They had / have a NSN and you could order them like other
parts. If you were doing serious operations and needed to spin the knobs as 
part
of the job, you hated the things. If you have one receiver on display skip 
it. If you get to have more than one receiver on display, buy all means add one 
to the shack
for looks. If the paint is falling off your dial counter, you may want to run 
a cover
over it.

Did you know you could also order red lights for the dial lights?
These were allowed in the Vans for field work.

Roger KC6TRU