Mea Culpa, you are correct, it is Armi San Paulo. I don't know what I was thinking - apparently I wasn't. Give me a break, I was on the road all day driving to Cheyenne for Hell on Wheels and was tired.
Now that he has edited the OP to say that there are date code and BP proof marks, I'll retract my thought that it might be a kit gun. I'll still say it's an ASM or ASP though
Fingers (Show Me MO smoke) McGee - AKA Man of Many Colts - Alter ego of Diabolical Ken; SASS Regulator 28564-L-TG; Rangemaster and stage writer extraordinaire; Frontiersman, Pistoleer, NRA Endowment Life, NMLRA, SAF, CCRKBA, STORM 327, SV115; Charter member, Central Ozarks Western Shooters
Cynic: A blackguard whose faulty vision see things as they are, not as they should be. Ambrose Bierce