A seven-foot slide rule. And its small cousin.

I work in a building filled with classrooms, some of which I never have occasion to enter. But between terms the floors get waxed and, during the waxing, a lot of what's inside comes out to wait. Thus this pair of giant slide rules.

I hope their presence means that someone is still being taught how to operate them. But I expect they are just artefacts of earlier methods of teaching, gee-whiz things for the students to think about.