Pistol Pacs had been specified by a “P” then the model variety of the revolver frame, then the barrel shroud form (blank) for standard, “V” for vent, “VH” for Vent HeavyAdditionally, it contains a 2 line roll marked shroud likewise. I know they transitioned to one line roll mark barrels, so possibly it's a transition gun or 1 pieced alo