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Art:

I have seen these  Concise circular slide rules around, their small size makes them handy, though with old eyes, somewhat hard to read.

Having played around with Gilson circular slide rules, their 8" dia. rules, in theory at least, are more accurate that the standard 10" stick type rule. With the C scale being outboard, the C scale has an effective length of 23+", as opposed to 10" on a stick rule. I remain curious as to why the circular slide rules never bacame popular. Possibly, their late arrival on the scene. In any case, these days slide rules have become curiousities, though Batteries Not Required ramains a virtue.

Alan

I remain curious as to how come the circular slide rules never gained the popularity of the stick rules.