Usually the split (compression) ring goes on the top bearing. And the non-split, circular ring goes on the bottom. Not a race, technically, it simply provides a smooth, correct angle, mounting surface to the corresponding angular cartridge bearing. Some forks are already machined or molded to accept the bearing directly. So check that before you start hammering this thing onto it!
Thanks Tim, it (the split ring) actually just slides on pretty snugly [I think you are right, it is just a mounting surface], I think when I tighten down the headset with a compression plug it will naturally line up flat on top of the fork. The standard crown has a bit of play between the ring and fork steerer tube. This is a tapered headtube, I have two lower crown races as above, two cartridge bearings, another top split ring a spring washer and a top dust cover. .