Ah, good ol' 5965s.
These were a higher-spec version of ... some really common tube which I
no longer remember. The Bendix G-15 was wholly based on them.
5965 is a computer rated 12AV7 with better balanced cutoff
characteristics, but generally worse for noise.
About 15 percent of the tubes in a G15 are 6197s, which are computer
rated 6CL6s.
--
Will