I don't think so. You can see the lower end of the grid wires in the first photo. There are also other internal connections between the cathode and anode structures, and maybe a couple of beam forming plates - so my guess is a beam tetrode of some kind, but my knowledge runs out at that point.
The 307A is a DHP (directly heated pentode) with a filament and 3 wound grids. This tube appears to have a cathode two wound grids and a set of beam plates. As suggested probably a 6L6 type variant, or maybe an odd heater voltage radio tube.
Thanks, George. Yeah, I did fail to mention those points in my post. That'll teach me to start posting before coffee! 😀
It appears to be a beam tetrode, has very similiar looking plate to some UK ATS25 807 equivalents, connecting heaters to an adjustable supply and measuring current could yeild a clue. Dial in 6.3 volts, if it draws 0.9A you have a 807/6L6 type tube most likely.
Glad you were able to ID that one! Sorry if I caused any confusion earlier; that's a really interesting tube I hadn't seen before. At least, I haven't ever come across one at a hamfest or antique radio swap meet.
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