Interesting frame.
They are indeed factory decals, and they're very hard to reproduce from this era as they're water-decals rather than vinyl. As such they have a difference appearance.
The Team Marin was a very lightweight custom quad butted steel frame in 1999 (which were painted pearl white), and this is one of them. I genuinely believe that the factory put the wrong Team decals on it too, as they're too original. It's definitely not Titanium, and that's easy to see from the photos, but it's kind of understandable that one late Friday afternoon the new guy in the factory put the wrong decals on!