SKALA PLASTIC SLIDE RULE This was the instrument of choice for calculations before calculators and computers. This is a basic slide rule with scales on one side only. An interesting blast from the past, now virtually an antique, certainly vintage! Solid plastic, scales on one side; a basic slide rule Good condition, with vinyl soft lined case. Instructions for how to calculate with a slide rule are readily available online Here are two sites: https://www.gutenberg.org/files/20214/20214-h/20214-h.htm https://www.sliderulemuseum.com/SR_Course.htm