(!!!!) (Recommended Pair) 5751 RCA black plates low hours/test like new 1961-1962 (2.5/2.5ma and 2.7/2.4ma) (Best Audio Grade 5751) (same Gm)
(!!!!) (Slightly microhonic Single) 5751 RCA Hewlett Packard black plates NOS 1968 (2.4/2.6ma)
(!!!) (Best Single) 5670 RCA NOS 1970 (13/10.6ma) (Highest mA and Gm)
(!!!) (SINGLE) 5670 RCA NOS "O" getter triple mica 1960 era used/good (6.6/7.2ma)
(!!) (Recommended single) 5670 RCA NOS 1969 (11.2/10.2ma)
(!!) 5654=6AK5 RCA Command Series black plate NOS 1968 (6.8ma)
(!!) 5654=6AK5 RCA Command Series black plate NOS 1968 (8.0ma)
(slightly microphonic) 5670 RCA NOS triple mica "O" getter halo 1961 (7.6/10.8ma)
