I'm told these can be put on the 144-148MHz amateur radio band without too much trouble. The tube lineup is 6AU6, 12AX7, 5763, 2E26, 6146, 4X150. Oprating at 500-1000V, this could pack quite a punch. High quality gear made for Uncle Sam. Looking at the images, that's not soot. It's tarnish on the silver-plated surfaces.Near the smaller tubes, the crystal oven can be seen in the lower left corner.