Originally Posted by seagrade

By the mid/late 1980s all Columbus fork steerers including and above Cromor had helical reinforcements. Whether the box the tube set came out of said SL or SLX the fork steerer and blades were identical in specification (as were the fork blade decals, as best as I can recall, with only the larger frame tubing decal differing).

SLX and SPX tubesets have rifling at the bb shell end of the seat tube, down tube and chainstays. The rifling is pretty obvious, much like in the fork steerer, if you can’t see any the frame isn’t SLX/SPX.