(!!) (#1 6S4A Pair) 6S4A GE Canada NOS same date codes (63ma and 68ma)
(!!) (#2 6S4A Pair) 6S4A Westinghouse Canada NOS black plates same date codes early 1960's (62ma and 70ma)
(!!) (#3 6S4A Pair) 6S4A RCA GAP/R Computor tube black plate used/good 1963 (64ma and 68ma)
(!) (#1 Best 6S4A PAIR) 6S4A RCA USA black plate NOS 1960's - 1970 (57.2ma and 56ma)
6S4 RCA USA black plate NOS 1953 (single)
6S4A Tungsol NOS "D" getter halo 1957 (single)
6S4A Tungsol NOS "O" getter halo (single)
