Tubes Asylum

Mullard GZ-34 F31 smooth plate ID

70.95.220.92

SoCalAl

I'd like to ID a Mullard F31 smooth plate. No etched code, taller flat top with a dimple, looks like a Philips with a fat base. Identical internal construction (to my eye) to another F31 date code B8D, this tube also has the dome top consistent with a Blackburn F31. The base on each are slightly different.
Is this other tube a Sittard GZ-34 with a fat base?

Edits: 03/07/23

Follow Ups:

RE: Mullard GZ-34 F31 smooth plate ID - dogscanskate 05:10:35 03/08/23 (3)
I see f31, B81 code on the tube at the left. Blackburn, 158/68 or 78 probably 31st week???
- RE: Mullard GZ-34 F31 smooth plate ID - dogscanskate 05:11:39 03/08/23 (2)
  1958/68 or 78
  - RE: Mullard GZ-34 F31 smooth plate ID - opalize 13:27:19 03/08/23 (1)
    "F31" type GZ34 is from 1958. However, I believe the question was regarding the GZ34 on the right, using that '58 Blackburn GZ34 as comparison.
    - RE: Mullard GZ-34 F31 smooth plate ID - dogscanskate 05:36:09 03/09/23 (0)
      My bad lol. You're absolutely right, I misread the post. I'm still laughing at myself for not reading the OP's post correctly.
RE: Mullard GZ-34 F31 smooth plate ID - opalize 19:09:02 03/07/23 (0)
Probably just a very faint etched code. Have you tried fogging with your breath? Scrutinized in full sunlight?

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