Hi Roland,
Have a look at the picture below, that I got off ebay, that shows a set of (weathered) OEM sunvisors. I've put arrows pointing out the screws I mentioned. If Heritage did not leave the screws accessible, I don't see how you can loosen or tighten the clamp on the hinge. Tightening that clamp sufficiently allows you to adjust the sunvisor so that it can rotate, but not flop around.
Without knowing if there is still a clamp in there, you could try pushing the hinge shaft in. Just be careful about that tab on the shaft, which, at a certain point of insertion, normally only allows you to push in the shaft in one orientation. i.e. if you feel too much resistance, don't force it to the point of damaging the sunvisor. If that happens, maybe you can call Heritage and see if they have suggestions.
On the other end, in the attached picture, you can also catch a glimpse of how the two pieces of the swivel fit together (circled). On the right end, you can just see the thinner internal pin going into the hollow swivel shaft. As I said the internal spring forces each end into a seat inside the sunvisor---assuming that is still in there. You could try poking a thin tool in the hole to see if you can feel the seats.
Without knowing just what Heritage has done internally, it hard to know exactly what to do.
Meyer