I have no theory about your 19-5. I have a 15-6 1990 or so vintage with some obvious factory issues. The left side edge of the trigger guard is much thicker than the right side and thicker than any of my other Smiths. The end of the trigger is blunt instead of tapered. The right side of the of the top of the trigger has deep machining marks that were polished out on the rest of my revolvers. So things like that can come from the factory when the QC guy is on break or hung over.