Here's hoping you get some competent advice.
I have one of these but am loath to pull the back off. Besides I won't be to the boat for some weeks now.
That said, if by " bare" you mean that there is a bit of copper showing, like 8 or so mm, then my guess is that it was once in a compression
fitting but pulled out.
Carefully look at the other connections to see if there is some evidence of this.
To my mind a alternator
should have two wires. But perhaps you have two coil wires and a separate ground wire?
I have had the little plate off just under where you are. That is the connection to the slip rings. I have a fairly beefy regulator
inside the boat that dumps excess energy into a resistor bank. So I'm not sure if you are getting AC or DC out of this thing.
EDIT....KJAMES. thanks for that dwg, going in my library!!!
go to pg 7, that yellow wire goes on the unused terminal. That must have diodes built into it, the blue things are the capacitors.