The 6J6 miniature double triode was used 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 cathode tube is coated on only part of the length and the grids and anode extend beyond the emissive area.
The control grids are close wound and pass flat across the cathode.
The thin glass tube envelope is 18 mm diameter and 46 mm high excluding the B7G base pins.
References: Datasheet & 1040. Type 6J6 was first introduced in 1956.