The ECF80 was designed as a mixer for operation up to 220 MHz. As 1950s television receivers tended to use the PCFnn 300 mA valves.
The valve is marked ECF80 and CV5215 showing that the CV specification is for the commercial device.
The triode is the oscillator and has to produce 5 V pk-pk signal. The screened pentode is the mixer. The valve has two cathodes so two independent valves are sited in the one envelope.
Unlike the Mullard ECF80 the anode of this exhibit is cut away at the ends and the three wire grids of the pentode can be clearly seen.
The open end of the pentode with the screen behind.
The thin glass tube envelope is 22 mm in diameter and, excluding the B9A base pins, is 49 mm tall.
References: Data-sheet & 1040 Type ECF80 was first introduced in 1954. See also1954 adverts.