http://Tube Rectifier.. (GE by Mullard / Sovtek)
the tube business is indeed a funny business,
GE buys tubes from RCA with the GE logo and vice versa...
Mullard ask Toshiba to make tubes for them, etc, etc,
having a tube that works well is good enough,
remember that cathodes of tubes gets depleted in use,
so that when transconductance is almost gone, you will see a lot of manifestations.....
so i look at tubes, not by who made them, but how much life is inside of them...