There's no need Bill to obtain that optical gadget to test whether your Columbus frame is SLX or not. This tube set only had the rifling in the bottom end of the steering column, as had most Columbus tube sets for years, and in the bottom bracket ends of the down and seat tubes. All you need to do is to dismantle and remove all the bracket and shove a sensitive finger up the open tube ends. Alternatively you could shine a small torch beam up them and make a visual inspection.
The tube set was introduced at the Paris Show in the autumn of 1983..and was available to builders in the course of 1984. Later in that decade Columbus introduced the TSX tube set. This one had rifling at the upper end of the down tube as well as in the top tube.
Hope that helps
Norris Lockley. Settle UK