The VX6025 is the MAzda prototype for the CV329 that was released commercially as the 6F33.
The suppressor grid has a short cut-off characteristic that makes it useful as a modulator etc.
This pentode has two open anode plates one each side of the central electrode assembly. The wire grids are rounded at the gaps in the anode and flat between the anode sheets. The suppressor grid is close to the anode with the screen grid close in to the cathode assembly. There is a diode connected to the suppressor grid to prevent blocking when the suppressor is driven positive. The close spacing of the suppressor grid wires generates the control characteristic.
A closer view of one half of the anode with connecting strap and open grid wires.
The thin glass tube envelope is 18 mm diameter and excluding the B7G base pins, is 42 mm tall.
References: Data-sheet & 1040. Type VX6025 was first introduced in 1949.