In my final few years at SSL in the late 1980's, I worked on the 5K console stuff (which is one of the reasons I left as it was so frustrating!). My memory has faded somewhat on this stuff and I can't help you with any schematics but, for the record, the 510 was a mono input module (520 was stereo), 503 and 533 were aux sends in different formats and 502 and 522 (stereo) were eq (not sure about the 542 but I guess it was a 242 type version). The 507 and 527 were pan modules.
Basically, the modules starting with 5 and then an 0 in the middle were mono types and the stereo versions were 52 plus another number. This doesn't directly help you but may make things clearer regarding the 5K module numbers. I'll add more to this post when I can find out more information and type it in red to show any changes. While I finish this, I'm trying to think of the compressor module numbers (damm).
Hope this helps a bit from Jim Lassen.
