<a href="https://en.wikipedia.org/wiki/Abney_level" class="extiw" title="w:Abney level">Abney level</a> or <a href="https://en.wikipedia.org/wiki/Inclinometer" class="extiw" title="w:Inclinometer">Inclinometer</a> made by <a href="https://en.wikipedia.org/wiki/Eugene_Dietzgen" class="extiw" title="w:Eugene Dietzgen">Eugene Dietzgen</a> Company of <a href="https://en.wikipedia.org/wiki/Chicago" class="extiw" title="w:Chicago">Chicago</a> circa 1936 (serial number 22098).  The scale is reversible.  As shown in the photo, it is set for measuring <a href="https://en.wikipedia.org/wiki/percent_grade" class="extiw" title="w:percent grade">percent grade</a>.  The reverse measures <a href="https://en.wikipedia.org/wiki/degrees_of_arc" class="extiw" title="w:degrees of arc">degrees of arc</a>.
<a href="//commons.wikimedia.org/wiki/User:Douglas_W._Jones" title="User:Douglas W. Jones">Douglas W. Jones</a>
<span class="int-own-work" lang="en">Own work</span>