6b4g tube Sylvania power black plate engraved valve 6b4 amp foil getter 1940's

power triode DHT for last stage audio amplifier old production made in USA 

one tube = 1 piece 6b4g tested TV7 = 54  (reference good at 38) 

tested also on tube tester Funke W19S Ia (mA) = 44mA  (reference good at 25mA) 

box 171