(!!) (2nd Best Pair) 6S4A RCA black plate NOS 1960's - 1971 (20.5ma and 20.0ma)
(!!) (Best Pair) 6S4A RCA black plate "U" getter NOS 1959 (21ma and 22ma)
(!!) (Pair) 6S4A GE NOS 1969-1970 (24.0ma and 25.5ma)
(!!) (Recommended PAIR) 6S4A RCA USA black plate NOS 1960's - 1970's (25.5ma and 28.5ma) (Highest mA and Gm)
(!!) (Recommended Pair) 6S4A Westinghouse black plate NOS -1963 era (20ma and 21.2ma)
6S4A GE Admiral NOS 1965 (27.5ma)
6S4A GE Canada NOS 1965 (27ma)
6S4A Raytheon NOS 1961 (20ma)
6S4A RCA branded Sylvania black plate NOS 1960 era (20.6ma)
6S4A RCA USA black plate NOS 1970's (19ma)
6S4A Sylvania NOS 1960's (20ma)
6S4A Sylvania triple mica NOS 1960's (20.2ma)
6S4A Tungsol branded GE NOS 1966 (21.5ma)
6S4A Westinghouse NOS 1963 (23ma)
