Harvey - it is solid brass. There is very minimal tarnishing, which I could handle. There are scratches, which appear to have just popped up. I worry if I strip it and refinish it, it will be uneven. I also don't know if the polish will apply unevenly with the scratches. If I have to replace it, it isn't a huge deal seeing as the belt is just an older Banana Republic belt; it would just be a pain in my ass since I actually like the shape of the belt and the buckle.
I know you asked Harvey, but i think i can help. I work with brass all the time (as a woodworker, brass tends to be used a lot for hardware). If the buckle is solid brass you can actually sand the belt buckle with very high grit sandpaper (the same kind that an auto finisher would use, P1000, 1500, 2000) or better yet, steel wool (it is graded from 0 to 0000, the latter being finer) to clean it and then polish it with brasso or even paste wax, it will come out looking great (with a slightly duller finish). If you want the higher gloss look, buy a can of lacquer (believe it or not, most "polished" metal is lacquered) and spray the buckle with a light coat (make sure you didnt wax it first). It should look like new.
As long as the buckle is solid brass, and as long as you sand off the finish completely, it will not look uneven.