The 7C was a great, perhaps the best sounding preamp of the mid 60s.
I bought one used around 1970. By the time I sold it the switches and potentiometers had started to get scratchy. Back then sealed switches and potentiometers were not used at least in consumer electronics. They may not have been available at all. By now unless the toggle switches and pots have been upgraded and power supply rebuilt it would be nothing more than a conversation piece.