Do you know what the 'Old Style' vs 'New Style' is in this model? Numrich lists some parts as available but does list old and new styles on some of the parts. Are old and new styles interchangable. Also, what is a 'Hammer Fly'. I wouldn't mind replacing the hammer on mine as either the single action notch has been ground or worn out. Cylinder stop, hammer, side plate, trigger guard, sear, are all parts that are listed as both old and new.