The 6J6 is an American design and this is a Cossor version with the same electrical characteristics. The 6J6 miniature double triode was designed for VHF signal amplification.
The construction has a common flattened tube cathode, with the control grids either side. The anodes are U channel sections either side of the central cathode.
The grids are wider than the anode as the wires are bent forward of the supports to get the grid close to the cathode.
A closer view of the construction. The grid supports are copper for good heat transfer. The anode can be seen to protrude forward of the grid supports. Effectively two planar triodes have been formed.
