Here’s a complete printset of the Venus Ibox, from 1984. It includes Ibox block diagrams, module and MCA block diagrams, and schematics for the MCAs and modules.
I’d bet my bottom dollar that there were ECOs after this version. But this hardware ran VAX/VMS and oodles of software.
Most of the page tops are faded. 75% of it is due to fading in the originals, and 25% is due to less-than-meticulous copying by FedEx.