Hi Freewill.
I don't think you'll be lucky enough to get a wiring diagram for an Eriba of that age. I think it might be a case of putting a tester on the wiring to sort out what does what.
I think I'm correct in saying that early Eribas were not produced with batteries fitted and as a consequence batteries were fitted if necessary by thier owners over the intervening years with all sorts of wiring arrangements dependent on their immediate requirements.
Do you know when your Eriba arrived Stateside and are you in touch with other Eriba owners in the USA?
As well as using this forum to find information and keep up to date with all things Eriba can I suggest you join this Facebook Group (Eriba Pucks in the USA)
https://www.facebook.com/groups/1509591689291126/
We are proud to say that it started as a group that with our support, broke away from our own Facebook Group (Eriba Folk) about 5 years ago and consists of a few hundred members that like you, own Classic Pucks and might be able to advise you regarding your wiring question.
Randa