12SN7GTA GE branded Westinghouse low hours 1960's (7.0/7.4ma)
12SN7GTA GE Honeywell gray plates used/good 1960's (6.0/6.8ma)
12SN7GTA GE NOS 1959 (7.2/7.0ma)
12SN7GTA GE NOS 1969 (9/8.2ma)
12SN7GTA GE NOS 1970 era (8.2/7.4ma)
12SN7GTA GE NOS 1974 (10/9.4ma)
12SN7GTA GE NOS 1976 (10.4/10.4ma) 1% section balance
12SN7GTA RCA coin-base branded GE NOS 1980 (12.2/12.2ma) 1-2% section balance
