I bought a collection of books a couple of years back, about 1500 or so. They had been picked over but there were still some gems - when I looked inside this one, I found the ‘free’ slide rule still inside it’s protective slip.

I’ll re-photograph it as soon as I get a new digital camera, the current one has a focussing issue in low-light conditions.

My own slide rule at College was circular, I dont recall ever seeing another one and unfortunately mine got lost during the intervening years. The circular rule was faster and gave more accuracy in a smaller form factor.

When time permits I’ll scan the pages of the book so you can recall those halcyon days before calculators arrived on the scene.