Also interesting that it seems to be hybrid.
Looks like the EQ section is solid state (maybe comparable to the MD16 EQ?).
What module is in photo 19? Germanium pre? Is that the same as those in the top row like on picture 19? They seem to have bass/treble controls (H + or -, so 'hoog' or high, I can't read the other letter) - seems like that could be echo sends or returns, to equalize that a bit (chamber echo), especially since they are more like trim pots.
I'm a bit puzzled by the row of valves in 13, because they are not on any kind of module or something, like the rest.
I'm just saying whatever comes to mind. I'm really interested to see how it really is, maybe with some schematics.