The Next Gen was an "updated" Dirtbike. Made stronger, but much heavier. I could be wrong, but I dont think S&M have ever offered a complete bike (apart from that 16" wheeled bike).
I got a Next Gen dirtbike in 1997 and it was one of the first ones. It was so heavy, not helped by the fact that its quite a short frame, that I hated it. It was the frame that made he have a rethink about riding such heavy bikes.
The first ones had that "Thrasher" sticker on the toptube, but they also had a very thin foil (chrome or black) downtube decal that just said S&MBIKES, like it was written with a pen. I had the decal on my cruiser for a while.