The 6J11 Compactron from RCA is a double pentode on a 12 pin base. We have seen it used as a tone generator and similar general purpose uses.
The edge of the grids can just be seen. The valves are in fact beam tetrodes. The strap in the foreground connects the two halves of the anode for one valve. Behind the anode strap is the beam plate. The visible grid is the screen grid. The inner control grid is wound on copper supports to aid heat dissipation.
The grid support for the screen grid of one of the valves.The two heater sections are run in series and are bridged across the top mica.
The 12 pin base.
The dome carries the type identification.
The wide glass tube envelope is 28 mm in diameter, and excluding the 12 base pins is 48 mm tall.
Reference: Data-sheet. Type 6J11 was first introduced in 1961.