For many years, most only had six or seven scales. Your email will not be published required. So it was marketing.
Eye-Saver "" puts the image on the retina and absorbs the actinic rays which produce "tired eyes. A lot has been lost by the use of calculators and computers. When did you start the website? Our only request is that you send digital photos of your class using the slide rules. Go to the Slide Rule Books. Interestingly, the first calculators that came out only did basic math, but not yet any of the scientific or trig functions like sine, cosine, tangent and inverse sine and square roots.