(!!) (Best Pair) 6CZ5 RCA black plate 1960's same build (49.5ma and 51ma)

1 pair) 6CZ5 RCA black plate 1960's 

1 tube) 49.5ma Gm=4950 (RCA branded Raytheon)

1 tube) 51.0ma Gm=4900 (RCA branded CBS

(you cannot sub a 6CZ5 for a 6973, see 6973 for more details)

Good NOS mA = 40-45ma

Good NOS Gm = 4500-5000

- Beam Power Tube