The upside-down mounted capacitors seem weird. They are particularly visible in the modulator board picture[1], but are also on other boards. Anyone know why that was done, or seen such assembly before?
It was a relatively common method in precision electronics.
There could be other reasons as well, e.g. if these were ceramic capacitors they might do that to avoid cracking issues. (Because ceramic capacitors drift a lot by themselves, a drift/precision explanation does not make sense)
In fact I remember being deliberately careful around them as they were easy to bend, when reaching in a tighter space to solder or adjust some variable resistors or capacitors.