(!!!) (Best Pair) 6S4A RCA black plate NOS "U" getter halo 1950's (25ma and 25ma)
(!!) (Best Canada Pair) 6S4A Westinghouse Canada NOS black plates same date codes 1965 (22ma and 24.5ma)
(!!) (Best GE Pair) 6S4A GE Canada NOS same date codes (21.6ma and 25.8ma)
(!!) (Good Value Pair) 6S4A RCA GAP/R Computor tube black plate used/good 1963 (22.5ma and 25.5ma)
(!!) (Recommended Pair) 6S4A RCA black plate NOS 1970 era (22ma and 24ma)
(!!) (Recommended pair) 6S4A RCA USA black plate NOS 1960's (22ma and 24ma)
(!!) (Recommended PAIR) 6S4A RCA USA black plate NOS 1960's - 1970 (20ma and 20ma)
6S4 RCA USA black plate NOS 1953 (21ma)
6S4A Tungsol NOS "D" getter halo 1957 (24.4ma)
6S4A Tungsol NOS "O" getter halo (22.6ma)
