The polished frame was the look Triumph originally intended for the bike. So your bike is especially kiff!!! (=cool dude!). It was only after some frame issues early on in Triumph's re-introduction to the US-market that the factory decided to paint the frame.
From what I've read there was a head tube issue with some of the painted early '97 T509/T595 frames. Although Triumph addressed the problem quickly, a rumor began after Triumph deleted clear coating the frame that all of the clear coated (glossy) frames were defective.
While there is a speck of truth to that rumor, such a broad generalization has been proven incorrect.