Still going through my tube stash and selling. I have some of these RCA branded 12AX7's. Made in Gr Brittain. They dont have the typical octagonal surround around the tube number, so I figure they are Mullard or Amperex or RFT ...? I have some long plate Mullards and Bugle boy. But nothing like these. I cant find any info on them. Any ideas? -short plate -Black plate -large 0 getter -The plates are a bit airfoil shaped which is also very weird. I made a sketch that's roughly the same.