A Mullard EF86 valve in working order and good condition.
The date code is L7B4 indicating it was made in Belgium in the M.B.L.E.(Mazda) factory (in 1957).
I find the British-made Mullards tend to be exactly on the factory specification and the non-UK Mullards like this have a bit more gain.
It has been tested on an Avo Mk3 Valve Characteristic Meter which can determine both plate current and transconductance and tests very strong (readings below).
Actual Readings
ia (mA) - 5
GM (mA/V) - 2.8
Data Book Specification
ia (mA) - 3
GM (mA/V) - 2.3
V10
