(!!!!!) (Best Single 1958) 12AX7=ECC83 Mullard UK "long plates" NOS 1958 (1.3/1.4ma)
(!!!!) (Best Bugle Boy Single 1959) 12AU7 Amperex Bugle Boy England (Mullard) long plates with "D" getter like new 1959 (12.4/9.8ma)
(!!!!) (Best Single 1956) 12AU7=ECC82 Amperex Holland "long-plates" large "D" getter with crossbar like new 1956 (9.2/8.2ma) (rare)
(!!!!) (Holland single 1958) ECC83=12AX7 Triotron Holland "long plates" with "D" getter halo like new 1957 (1.1/1.2ma and Gm=1700/1700)
(!!!) (Recommended Single) 12AX7 RCA "tall gray plates" and "D" getter halo branded Raytheon used/good 1950's (Gm=1900/2100) (1.3/1.7ma)
(!!!) (SINGLE) 12AU7=ECC82 RT Radio Technique France long plates 1958-1959 (11.6/9.8ma) (close Gm)
(!!!) 12AX7=ECC83 Mullard UK "long plates" with "D" getter used/50-60% (0.6/0.7ma Gm=900/1000 - low Gm) (mC1 series)
(!!) 12AU7A CBS black plates NOS 1960 era (9.5/11.8ma)
ECC82=12AU7 Siemens Halske "Long Ribbed Plates" and "O" getter NOS 1958 (10.4/11.8ma)
ECC83=12AX7 Mullard UK BVA long plates "O" getter like new 1958 (f91 series) (1.2/1.2ma)