12AX7 tube ecc83 Semens Germany preamp tubes quad valve 1960's silver grey plate
tested TV7D/U (reference good at 32/32)
tube 1 = 46/42 code i62 ≠ 2k grey plate ribbed , silver corner , O getter with 2 support
tube 2 = 49/49 code i62 ≠ 4b grey plate ribbed , silver corner , O getter with 2 support
tube 3 = 53/50 code i62 ≠ 3j grey plate ribbed , silver corner , O getter with 2 support
tube 4 = 48/52 code i62 ≠ 4b grey plate ribbed , silver corner , O getter with 2 support