Well, here's a tasty pair of device both clear glass "coke bottle' KT66 in GEC livery.
The device carries markings in excellent white ink, a classic GEC/M-OV military cartouche with a date code of YB which equates to February 1967 and factory code Z which indicates Highgrove manufacture. The obverse sides carry perfect elliptical two tone blue and white GEC decals. The brown low loss micanol bases are both tight to the valve envelopes.
This device has been tested using our AVO VCM163 against the specification for 100% emission of anode current, Ia =63 mA; mutual conductance gm = 6.3 mA/V @ At Va = 250V Vg = -15V.
The results obtained were:-
Ia1 = 90 mA.
gm1 = 6.0 mA/V.
Ia2 = 93 mA.
gm2 = 6.1 mA/V.
These test figures indicate not only a very strong pair of devices which EXCEED nominal specifications but also are a supremely matched pair - not to be missed.