Not a No. 5 pacific since it is a cast frame, 3 line address is nearly always a cast frame.  It is a straight grip like a No. 5 but 5's were forged frames, 2 line address, and had double set triggers.  Most likely a No. 2 action?
Phil

I say it's a #2 as I see a screw in the lower position for the reversible firing pin. The #3 Ballard didn't have this feature. Then of course we don't know if the block and action serial numbers match.

JerryH

Until we know more about the particulars of this rifle(receiver) all is speculation. As with Ballards, and most single shot rifles, almost any thing is possible. No one has said this is a cast action, forged action #2s do exist, nor what it is chambered for and as Jerry stated, it could be a conglomeration of parts. Regardless, it is a worthwhile action to have, given an appropriate price. If all the numbers match, then it is most probably a number two. We will have to wait for more information, x-ray vision, or Divine intervention.

Thanks everyone It is part of the estate from Reverend Al and they are selling off his single shots.