This exhibit is the Mullard ECC82. Designed as audio and general purpose triodes, two independent valves exist in the envelope. Each half is sensibly equivalent to one EC90 triode.
An amplification factor of 17 is quoted, which is much lower than that for the pin compatible ECC83 at 100.
In television receivers the ECC82 was used as frame and line timebase multi-vibrators, AGC circuits and driver stages. It was as multi-vibrators that faults would most often develop.
This exhibit is British Made and carries the older Mullard logo as well as the BVA logo, the Type designation features the Monotype Spartan font with small pointed serifs.
The two piece anodes are stitched together and tabs top and bottom locate in slots within the mica discs.
The anode face view.
The thin glass tube envelope is 20 mm in diameter, and excluding the B9A base pins is 48 mm tall.
References: Datasheet & 1040. Type ECC82 was first introduced in 1951.