(!!!) (Recommended Pair) 7591A GE coin-base NOS original boxes 1970's - 1981 (63ma and 65.2ma) (can make a quad with another pair)
(!!!) (Recommended Pair) 7591A GE coin-base NOS original boxes 1981 (62ma and 62.5ma) (can make a quad with 1st pair 63/65.2ma)
(!!!) (Recommended Pair) 7591A GE coin-base NOS original boxes 1981 (79ma and 83ma)
7591 Tungsol used good 1963 (55ma, Gm=8100)
7591 Westinghouse branded RCA NOS 1963 (51.5ma, Gm=9050)
7591A Sylvania branded RCA used/75% 1968 (51ma, Gm=7,600)