The good folks at the Australian Pinball Museum let me dig through their archives of manuals and I turned up something that isn't conclusive but is definitely suggestive of the machine! It's just a partial schematic, looks like it's mainly about diagnostic indicator lights rather than something more complete. I spent quite a bit of time and this was the only one I could find that seemed useful. The date seems about right and but the title of the doc is the most interesting part. So who knows?

Now this is interesting! That model of node board (based on my extremely-not-an-expert analysis) seems to be a fairly common one, but I can't find other references to the "ITO-A" bit here. That, along with the date and company all matching up, definitely could be some evidence of the machine.

Anyone here know anything more specific about this stuff? I wonder if they'd have tried to work in any easter eggs and design jokes in the boards itself - like spirals in the circuits and such.