76 S tube pair fivre italy preamp tubes amplifier black engraved base

rare version " S " type , tubes are tested = 84 / 68 ( reference good is 36 ) on tube tester TV/D/U  military instrument calibrated ,

tubes are both black rugged ruggedized smooth plate , black base engraved with codes CT40 & CT64 

one tube has the oldest Fivre logo badge RED but it's partially erased 

tubes are not matched pair but  with the S type , they are extra rare , very hard to find 

box 79