The QV05-25 from Mullard is another example of the design known as the 807. The QV05-25 is a beam tetrode. and this example was made in Canada. The distinctive feature is the fluted top cap.
The parameters given are for single ended use. When used in a class AB1 as a push pull pair with 600 Volts on the anode an output power of 65 Watts was normal.
The QV05-25 was an HF RF amplifier and used in many designs in the 1950s. As a transmitter power amplifier (shown in the lower table) operating in class C producing 40 Watts of RF, it would need a pair of 807s in push pull to generate the 20 Watts of audio required to fully modulate the valve.
The oval screen below the lower mica is a feature of the 807 design.
The additional support struts are connected to the lower screen.
The classic envelope is 51 mm in diameter, and excluding the UX5 base pins is 127 mm tall.
References: Datasheet & 1040. Type QV05-25 was first introduced in 1947.