The ring on the left looks like a crown seat located one and not a compression one. If I am correct the split in the left ring allows for some tolerance of the ring's fit onto the crown seat (carbon frames and forks are not known for their maintaining tight dimensional tolerances). It's wider angles lower surface will locate the lower stack's bearing, likely this angle is a 45* or 36*, the two most common seating angles for headsets. The right ring has a much steeper angle that is across the entire ring's height. This is far more like the usual compression ring that fits within the upper stack's bearing seating part (which also will have that 45* or 36* angle). The steep angle on this ring better centers the seating part and keeps it from rocking. (The crown ring has a flat surface is sits on as well as the vertical surface in the steerer. The upper has only the steerer so need greater contact with that surface). Andy