Are you asking about Series basses? They are quite different than the other Alembics.
The normal compartment has a lot of pots and connectors. A Series I would have 4 pots, but there are also Q-switches, the 5-pin stereo output jack, and a very complicated 1/4 jack.
On the other side of the body, there's a the preamp and EQ boards. There's a tunnel between the compartments with a lot of wiring.
There's also a third, smaller plate in the center block that holds a pair of 9V batteries that power the electronics when you're not using the 5-pin external power. Sometimes it's round, sometimes it's square.
There was a period where Series bodies were quite thick, so the electronics were all on one side.
And, as you probably already knew, the Series basses are semi-hollow contstruction - the neck/center block runs the entire length of the instrument and the top and back are 1/4 thick, but they bandsaw most of the center core out. This is only really visible when the plates are off.
David Fung
