That early version of the Facile Princeps action is mentioned on page 174 of Graham Greener's book. He describes the FP action as using a hook on the barrel lump or a sliding rod. His description of a hook on the front barrel lump matches the photo you provided. I'm guessing it was built by Greener and merely retailed by Reilly. The action is certainly filed up like Greener work of the period. Greener did use bolted dolls head fasteners like yours, not just the more common crossbolt. The top lever? Who knows. Maybe just tweaking Westley Richards. The patent is listed as 930 of 1880.