To me, the Philadelphia Arms guns are the most interesting in regards to the Parker connection. It has so many features that are similar to Parkers.
The hinge pin, the frame sculpting, the engraving. The forend latches and irons on these guns look to have come right out of a Parker parts bin. Even the rib matting and makers mark is almost identical, right down to the arrows on each end of the roll stamp.

The Sterlingworth guns' similarities end at the hinge pin.

B.Dudley