I'd like to ID a Mullard F31 smooth plate. No etched code, tall 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?
