Columbus refers to the augmentation to their steerer tube as "helicoidal reinforcement," not "splining" or "splined."

You might take your query over to CR where you can and strut your little knowledge to the likes of Merz, Sachs, Fattic, and others? Can put in a word for you with Dale. If nothing else, it will be amusing for a minute.
Someone there may ID your example? Not interested in helping because you are Butted. (sic)

(How can you not know whether it's welded or brazed?)