The QQZ03-20 from Mullard is the quick heating form of the QQV03-20A double beam transmitting tetrode.
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.
The heater runs at 1.6 Volts and 4.25 Amps. The surge at power-up is sufficient to raise the cathode to an operating temperature such that 70% of rated output is available in 0.7 Seconds. Note that the pins are connected to the electrodes with copper straps, probably because of the surge of power on transmit.
In addition to use as transmitter power amplifiers the upper frequency of 600 MHz made them popular for frequency multiplication.