The EL822 output pentode is specified for video use, i.e. 5.5 MHz and wide bandwidth DC to 5.5 MHz. The impedance is high and so is the amplification factor is high. This valve with its 6.3 Volt heater may be designed for professional video.
This exhibit was made in the UK and has yellow lettering. The yellow paint was introduced for 1969 to celebrate 50 years of the Mullard company.
The control grid copper supports have heat sinks at the top. The notch in the anode reveals the tops of the three wire grids.
The suppressor grid is also wound on copper supports, but not the screen grid.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 70 mm tall.
References: Data-sheet & 1040. Type EL822 was first introduced in 1962.