As Arte Johnson used to say in his WW2 German costume, veeerrry interesting. Those R390s were Collins, others were even made by Ford, and darn if I can remember which Army "mobile" station used the Collins 30L1 KW amp. Funny thing about WW2 military radio, anything that could be moved with a fork lift was mobile. Remember the TV series 12 O'clock High? Every bit of the base radio station was authentic right down to the BC610. The last R390s I saw in the Surplus Sales of Nebraska catalog were "demilitarized" with the radium dial dB meters removed, (VU meters work but look so phony) they stopped glowing long ago but the paint is still slightly radioactive. Laws are often quite senseless, radium is an alpha emitter. Alpha particles consist of 2 protons & 2 neutrons with low penetration stopped by a few centimeters of air or skin. That being the case there's no way they can penetrate the glass front or metal case of the meters that were in those intact receivers I restored. Unfortunately very little US military radio surplus is to be had since it now is all classified and instead of the surplus market it goes in the shredder. The last I saw on the market was British some years ago, man packs were of the Clansman series. I remember the 60s before Manhattan's Mercantile District was razed to make way for the World Trade Center Complex. In the heart of it was Radio Row where I had to step over and around tons of surplus radio gear on the sidewalk to get around. If Archie Bunker was a ham he and Edith would have sung a very different tune!