The E80CC is a special quality double triode introduced by Mullard in 1957. It has a ruggedised design and was made to have a long service life with a lack of microphony courtesy of the electrode cage's torsional rigidity. The design purpose was for computing, switching and scaling with each of the two triode sections within the envelope - box anode ala CV4004 - being of frame grid construction and posessing a noise factor of 4.6 dB which makes it eminently suitable for RF, IF as well as audio usage.
Many valve amplifier affectionados use the E80CC as a low distortion, low microphony substitute for the ECC82 allbeit with slightly different operating parameters and double the filament current requirements. Personally, I feel that these gold pinned beauties are a scarce and supremely high performing device rewarding users with an ultra long service life with a smooth deep uncoloured sound stage - very nice indeed.