This matched quad of GE 6SN7GTB dual triodes was tested on our Paul Hart-calibrated TV7/U for shorts, gas and transconductance. There were no shorts or gas.
Transconductance measured 56/56 for Tube One and 58/61 for Tube Two. Tubes Three and Four measured 58/61 and 60/62, respectively. (Minimum (65%) is 50/50.)
They have horse shoe getters; copper support rods; great flashing and 60-13 188-5, 56-39 188-5, 59-13 188-5 and 57-26 188-5 date/factory codes, respectively.
I have played them in my Radio Craftsmen RC-2 monoblock amplifiers (see Pictures Six through Nine) and they sounded great. They are dead quiet when the volume is muted and have excellent frequency response, sound-staging, and dynamics.