(!!!) 6S4A RCA black plate NOS 1960's faded printing (20ma)
(!!) (Best GE Pair) 6S4A GE NOS 1961-1962 (23.0ma and 23.6ma)
(!!) (Best RCA Pair) 6S4A RCA black plate NOS 1967-1968 (23.0ma and 24.2ma)
(!!) (Pair) 6S4A GE NOS 1957-1961 (22ma and 22ma)
(!!) (Pair) 6S4A GE NOS 1969-1970 (24.0ma and 25.5ma)
(!!) (RCA Pair) 6S4A RCA black plate NOS 1969-1973 (21.0ma and 22.2ma)
(!!) (Recommended Pair) 6S4A Westinghouse black plate NOS -1963 era (20ma and 21.2ma)
6S4A GE Admiral NOS 1965 (27.5ma)
6S4A Raytheon NOS 1961 (20ma)
