Demonstration <a href="https://en.wikipedia.org/wiki/inclined_plane" class="extiw" title="wikipedia:inclined plane">inclined plane</a> apparatus, used in science education probably around the early 20th century, on display in the <i>Schulhistorische Sammlung</i> (School Historical Museum), Bremerhaven, Germany.  The slanting metal track serves as an inclined plane.  The small brass wheel on the track <i>(left)</i> with the large weight hanging from it serves as a load, which is pulled up the plane by the cord attached to the small weight <i>(right)</i>. Since the larger weight can be pulled up the plane by the smaller weight the inclined plane demonstrates <i>mechanical advantage</i>.  The angle of the track is adjustable, to change the mechanical advantage.
<a href="//commons.wikimedia.org/wiki/User:Hgrobe" title="User:Hgrobe">Hannes Grobe</a> (<a href="//commons.wikimedia.org/wiki/User_talk:Hgrobe" title="User talk:Hgrobe"><span class="signature-talk">talk</span></a>)
CC BY 3.0
own work, Schulhistorische Sammlung Bremerhaven