I have one at home, which is the one we had to buy to use in highschool. In the math classrooms we had a 6 feet version that could be mounted on the blackboard such that the teacher could used for instruction. See for a picture on the Dutch page https://rekenlat.barneveld.com/rekenliniaal.htm

These TMSLs were also reasonably common in classrooms in the United States in the 1950s.

Two Meter Slide Rule