Attic find, pretty rare item on ebay. As you can see in the video it still works great. Does need cleanup but otherwise no major issues for a 40 year old analog synth.Reading online most of these were factory assembled and looking at the tidy soldering and wiring I'd say this one was as well. It does appear to also have the second bus of the keyboard wired, hence the extra big connector (did not test).
There is a tons of materials on the web for this one. Here are a few interesting docs:
Let me know if you have any questions.