Thanks Duck, Those are 1/8" shaft solid copper rivets ("round head"). I just drill holes (#30 bit, 0.128") for a slip fit.
I'll groove a shallow ring into the ends and use epoxy so they'll lock into the joint and add strength (1" long).
I also use 1/4" long for places where they are purely show.
Use to be that the round head were all I could find at a low cost, but now I can find flat head (like a box nail) and countersunk like wood screws for a flush fit.