Rebonjour
Probes, as mentioned the P600x series was used at the time.
The later probe's had wider BW but lower compensation C range.
A point of history...Stanley Kubrick's 2001: A Space Odyssey had a scene of astronauts David Bowman and Frank Poole, troubleshooting the AE -35 LNA, with a Tektronix P600x probe. No scopes though
Recommend 1980s Tektronix circuit concept books
Oscilloscope Probe Circuits and
Probe Measurements
536: a unique scope, used throughout the 1960s. So, at Marantz, Sid's , tube amp, preamplifier, tuners, 1,5,7C, 10B, were designed using 536. I was assisting Sid, later at Sequerra, I marveled at the simplicity of his technique.
Jon
Jean-Paul