5691 RCA Red Base Black Plates used 1948 (2.2/2.4ma) (Gm=62% and 75%)
6SL7GT Brimar NOS black base black plates 1950's (2.2/2.4ma) (slightly microphonic)
(!!) 6SL7GT Sylvania NOS branded Westinghouse tall bottle 1955 (2.8/2.7ma)
(!!!!) (Recommended Single) 6SL7WGT Sylvania brown base round black plates "D" getter tests like new 1957 (2.1/2.3ma)
(!!!) (Best Pair) 6SL7GT RCA NOS black plates gray coated glass 1959-1960 (2.2/2.3ma and 2.2/2.3ma)
(!!!) 6SL7WGT Sylvania brown base round black plates like new 1955 no printing (2.6/2.8ma)
(!!!!) (Recommended Pair) 6SL7GT Sylvania short bottle chrome top NOS 1953-1954 (2.5/2.4ma and 2.5/2.7ma)
(!!) (slightly microphonic pair) JAN-6SL7GT=VT-229 RCA NOS and like new 1940's (2.5/2.4ma and 2.4/2.6ma) 1-3% matched
(!) (SINGLE) 6SL7GT RCA round black plates NOS 1970 (2.0/2.1ma)
(!!) (single) 6SL7GT RCA NOS black plates gray coated glass 1959 (2.0/1.7ma)
(!!!!) (Best Single 1944) 6SL7GT Sylvania round black plates NOS 1944 (same build as VT-229) (2.1/2.3ma)
(!!!) (Recommended Single) 6SL7GT RCA NOS 1962 (2.5/2.7ma)
(!!!!!) (Best Value Single) JAN-5691 Philips by Sylvania black plates NOS 1985 (2.4/2.6ma) (Best 6SL7GT sub)
(!!!!!) (recommended pair) JAN-5691 Sylvania black plates NOS 1977 (2.8/3.1mA and 2.5/2.9mA) (Best 6SL7GT sub) (same internals as 5691 red base)
(!!) 6SL7GT Sylvania NOS 1960's (2.6/2.2ma) (Eddie Current)
(!!) 6SL7GT Sylvania NOS branded Zenith 1950's tall bottle (3.0/2.9ma)
(!!) 6SL7GT Sylvania NOS tall bottle 1955 (2.0/2.2ma)
(!!!) (PAIR) 6SL7GT Sylvania round gray plates NOS 1952 (2.1/2.4ma and 2.3/2.5ma) (same Gm)
(!!!) (Slightly microphonic Single) 6SL7GT Ken Rad NOS 1945 era (2.6/2.3ma)
