The VP13A is a variable μ amplifier pentode, and features the Ct8 side contact base.
In use the variable μ pentode was designed for AGC controlled stages of superhet receivers, the RF and IF sections. The control grid is taken to the top cap for maximum isolation between grid and anode circuits.
The metallising has broken away from the top of the glass revealing some of the inner details. The anode looks to be a ribbed cylinder. Above the anode is a top screen and above that can be seen two radiating fins connected to the top supports of the control grid.
The top screen and the wire connecting the control grid to the top cap.
The classic envelope is 42 mm in diameter, and excluding the Ct8 base pins, is 101 mm tall.
References: Data-sheet & 1043. Type VP13A was first introduced in 1934. See also1934 adverts.
