Heath by Mullard ECC83 12AX7 F92 Long Plate Blackburn Tube TV-7B/U tested 42/42

This desirable early1959 F92 Blackburn Mullard features the sought-after17mm long black ribbed plates ,single halo getter, and genuineBlackburn etched factory codes (F92 / B9C). These construction details identify it as an authentic early Mullard long-plate tube and distinguish it from later short-plate versions.