This exhibit is a russian made valve imported to the UK by Zaerix. It carries the 6BL8 and ECF80 designations.
The ECF80 was designed for operation up to 220 MHz. As 1950s television receivers tended to use the PCFnn 300 mA valves, the production of this valve with a 6.3 Volt heater suggests that it was aimed at the professional VHF communications market.
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.
The ECF80 designation with Made in USSR in English.
The triode on the left and larger pentode on the right. This is a true pentode with three wire grids. The later ECF82 was in fact a triode Beam tetrode.
The thin glass tube envelope is 22 mm in diameter and, excluding the B9A base pins, is 48 mm tall.