Thank you John for the update,
The picture of the window, with one side chisled flat. I can answer that for you.
The iron pins sticking out had a door or gate that would swing on them. The small flat areas on the arch stone and oposite side indicate that when closed, it would be flat against the stone there. When opened, it would not open all the way as the stone on the hinge side would keep it from going against the building. It would be my guess that chisling it flat occured later when it was decided that the open door/gate needed to be against the building and not sticking out. A longer offset piviot would have been needed to allow clearence without chisling the stone flat.
Phil