DEAD PARKERS

I believe I saw a listing there- a gent has two Parker receivers- one pre-1905 patent date, not sure about components or if it is just the receiver and top lever- the other may have all working parts and is post-1905 patent date- he listed the serial numbers- To determine the frame size, you would need to measure the between center hole distances of the firing pin holes, is that right? Always wondered why the frame size for Parkers was on the barrel lug bottom face, NOT on the frame-

I have an old HBS Crescent "mini-boat anchor" sidelocked hammer 12 gauge receiver to hold down prints, papers, misc on my gun bench- I think I'll maybe buy those Parker receivers and use the emptied one instead, and relegate the Crescent to a goose decoy anchor--