Originally Posted by
Condorino
...I took a quick look at the steering tube without any clear results however I am not sure that I know what I am looking for exactly. I was wondering if someone on the thread might have a mid-60's Columbus built frame at hand that is not built up . . . that might be able to post a few pictures of the defining markings that T-Mar has described. If possible . . . my thanks in advance.
Here's what the five helical ridges look like on the inside of the bottom of the Columbus steerer tube. They are quite narrow (3.5mm) and very thin (0.35mm). The logo on the outside of the tube looks just like the oval and dove on the tubing decal. Photos courtesy of members JunkYardBike and JohnDThompson.