What I am referring to is the way the bar is rounded around the hinge on a rising bite action in much the same way as a hammergun is filed.
There are "cheeks" formed behind the hinge. Most hammerguns with this treatment have a full semi-circular contour to these cheeks but the Rigby contour runs straight up to the flats.
The mastercam images above do not show that contouring.
Seems to me that some are more pronounced than others. Not sure if that is a function of year or caliber/frame size or just coincidence.