Has anyone heard of or seen a 6" 15-1 in nickel? Collectors guide says 6" wasn't offered till -5? I'm looking at a 6" 15-1 in nickel and it has the trigger guard screw square butt. Any info will be appreciated. I've read there was a very limited run of ss 15's special order how can I tell the difference without hands on? Trigger and hammer are silver toned also. HELP