It's true that there are two US versions of Sonic Spinball. As goatse (nice name, pal ) says, the original version made use of the theme song from Sonic 1 and 2. The developers discovered that the rights to the song were not owned by Sega, but were still held by Dreams Come True, the band that did the music for the first two Sonic games. Spinball composer Howard Drossin wrote a new theme and redid a couple other tracks, but copies of the game with the original music were accidentally released in "limited numbers." The European and Japanese versions of the game are based on the second US version.

I'll have to check, but I don't think my copy is the original version. Also, I don't think anyone knows for sure how many of these copies made it out, and I don't think there is any way to distinguish between them, besides actually playing the game. In any case, there doesn't seem to be any real demand for the original version--checking eBay shows many listings for Spinball, but I didn't see any that were advertised as being the original release.