The 8136 is a beam tetrode from the American General Electric corporation but is referred to as a pentode.
The anode is the dark plate at either side of the envelope and joined with a centre strap. The bright plate to the right of the anode is a beam forming plate. Centrally is the cathode and grid structures.
In close-up the inner structure is revealed. The two halves of the anode can be seen. The central grid structures are at 45 degrees and both grids are visible. The beam plates are spaced half way between the screen grid and the anode.
The construction is like a beam tetrode version of the EF91.
The thin glass tube envelope is 18 mm in diameter, and excluding the B7G base pins is 47 mm tall.
Reference: Data-sheet. Type 8136 was first introduced in 1958.