Pickett model N4ES Log-Log Vector Hyperbolic <a href="https://en.wikipedia.org/wiki/slide_rule" class="extiw" title="w:slide rule">w:slide rule</a>, reverse side, from author's collection.
<a href="//commons.wikimedia.org/wiki/User:ArnoldReinhold" title="User:ArnoldReinhold">ArnoldReinhold</a>
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<span class="int-own-work" lang="en">Own work</span>