Correct me if I'm wrong, but those tips look angled, which would make it one of their "ZR" tips. I think those were introduced later. The original was a straight "bull nose' tip. Their older exhausts were shiny all the way through the pipes, whereas the newer ones had matte piping. This is all before they changed to all round mufflers of course.
I've had 2 of them and neither one (driving in the rain) has shown deterioration in the pipes like that. Someone set me straight.