Great buy for those who have good eyes or are myopic: they can then use the circular slide rule (by removing the glasses for myopia). For others I recommend buying a rather slide rule in Concise (Japanese brand) is still beautiful slide rules circular large diameter (over 10 cm). I note that the slide rule works without batteries. It means that if one day for one reason or another you are deprived of batteries you can do basic calculations (addition, division, extraction of square roots, trigonometric functions to see products that Amazon would also Concise well inspired to broadcast). You may say why bother? In case of serious crisis linked to the turmoil the new world order we are not forced to fall back in the hunter-gatherer, is not it?
