(!!!!) (Best Pair) EL84 Mullard UK NOS 1969 and 1972 (50.4ma and 53.5ma) (close Gm)
(!!!!) (Best Single 1975) 12AX7=ECC83 Mullard England ribbed plates NOS 1975 (163 Series) (1.3/1.4ma and Gm=1800/1800)
(!!!!) (Recommended Pair) 12AX7=ECC83 Mullard England ribbed plates NOS 1966-1970 (163 Series) (1.1/1.0ma and 0.9/1.0ma)
(!!!!) (Slightly microphonic single) 12AX7=ECC83 Mullard UK branded Philips ribbed plates NOS 1962 (161 Series) (1.0/1.2ma and Gm=1600/1650)
(!!) (Recommended Single) EL84 Mullard UK branded RTC England NOS 1977 (40.4ma)
EL84 Siemens Halske Germany NOS 1967 (45ma)
EL84 Siemens Halske Germany used/70% 1969 (34.5ma)
EL84 Siemens Halske Germany used/tests like new 1971 no printing (48.2ma)