(slightly microphonic) 6SN7GTA GE NOS 1952 copper grid posts (7.4/10ma)
(slightly microphonic) JAN-CHS-6SN7W Sylvania "SHORT BOTTLE" used/good 1945 (7.0/7.6ma)
6SN7GTA CBS NOS Black Ribbed Plates similar to RCA early 1950's (8.3/8.6ma)
6SN7GTB CBS black base black plates side-getter, the same shape as Sylvania 6SN7GTB used/good 1961 (7.5/8.0ma)
6SN7GTB RCA used good 1960's (6.4/8.2ma)
