I've got an original Mk1, scrolly wheel actually scrolls, only accepts fire wire, 5GB iPod. The very first one, and the lowest spec one at that.
My mate got it for me cheap when I was at Uni, he did a summer internship with Apple UK and it was part of their old demo stock sold off cheap. So not only it is Gen 1 iPod, it's an ex Apple Gen 1 iPod. Still in the original box with iTunes CD and everyfink.
It's worth fuck all