steerer tube id help sorted

Hi, a question for the Retrobike hive-mind .

I've got a pair of Tange Switchblades that are fitted with a later, 'framebuilder' made, 1" threaded steerer tube. The base of the steerer where it is clamped into the crown has 5 distinct raised internal ridges (rifling?) running up about a quarter of the length. Am I right in thinking this is a trait of Columbus SLX or are there other tubing manufacturers who employed this type of internal strengthening?.

Thanks for your thoughts and time. Matt

........a couple of hours of idle googling later and I have my answer, both Columbus SL and SLX tubesets have steerers with internal ribbing.