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