(!!) (Recommended Pair) 12B4A GE NOS 1960's - 1970's same build (30ma and 30.5ma)
(!) (Recommended Pair) 12B4A RCA NOS 1963 (40ma and 41ma)
(!) (Recommended Pair) 12B4A Sylvania NOS 1960's (26ma and 27ma)
(!!) (Recommended Pair) 12B4A GE NOS 1962-1970 (36ma and 36ma)
