The QQV03-20A is a double beam tetrode transmitting valve introduced in the early 1950s, this example was branded Zaerix and made in the GDR. The GDR being the German Democratic Republic - East Germany.
Following the European pattern, a central flat cathode is surrounded by a split control grid (one half per valve), a common screen grid is wound next. The two beam forming plates can be seen either side of the central assembly. The anodes are finned for good heat dissipation and clearly separated from the central structures, the anodes are brought out to pin like top caps.
In addition to use as transmitter power amplifiers the upper frequency of 600 MHz made them popular for frequency multiplication.
The anodes are supported only at the top. In the central column the screen grid winding is just visible.
In this image the grid wires are easier to see. Both grids are wound to the same pitch and aligned such that the screen grid blocks the direct path from the control grid to the anode.
The top glass does not have the sintered appearance of the Mullard QQV03-20A.
The base glass is also clear.
The wide glass tube envelope is 43 mm in diameter and, excluding the B7A base pins and top pins is 52 mm tall.
References: Datasheet & 1040. Type QQV03-20A was first introduced in 1952.