"See the pretty label. UK does not use the 12AX7 code."
I'm thinking they did. There's many Brimar tubes out there similar to that 12AX7. For over 20 years, I have had the remainder of a Brimar 12AT7 bulk pack. Originally had about 65 of a 100 tube box. They look like the 1955 red label in the Brimar picture here. The ragged old box also has the red Brimar name printed just like the tube.
https://www.tubeworld.com/12at7.htm
For years, I had no idea what they were, then found that picture. After finding it, I let a few friends try the tubes, and no one would give them back. They wanted to keep them because of how good they sounded. There's also a reference on Brent Jessee's site for this tube under 12AT7. The tube is a black plate with a square getter, and he said made for the military. That seems to make sense because of the bulk box of 100 and no individual boxes.
I'm thinking they did. There's many Brimar tubes out there similar to that 12AX7. For over 20 years, I have had the remainder of a Brimar 12AT7 bulk pack. Originally had about 65 of a 100 tube box. They look like the 1955 red label in the Brimar picture here. The ragged old box also has the red Brimar name printed just like the tube.
https://www.tubeworld.com/12at7.htm
For years, I had no idea what they were, then found that picture. After finding it, I let a few friends try the tubes, and no one would give them back. They wanted to keep them because of how good they sounded. There's also a reference on Brent Jessee's site for this tube under 12AT7. The tube is a black plate with a square getter, and he said made for the military. That seems to make sense because of the bulk box of 100 and no individual boxes.