Silver Supporting Member
.....Just found a tube in a small stash of 12A*7's. The only thing I can read on it is: B6A3 etched on the side. Above that looks like: 163 or I63. The only other thing is what appears to be a BACKWARDS "J" centered on the bottom between the 9 pins. Round halo thing on top. Plates are "laddered". so to speak. Any educated guesses? Maybe it's useful.