Postcard of <a href="https://en.wikipedia.org/wiki/en:Benjamin_Baker_(engineer)" class="extiw" title="w:en:Benjamin Baker (engineer)">Benjamin Baker's</a> human cantilever bridge model.
Unknown photographer for Benjamin Baker.
Uncertain, between 1882 and 1904 (when published in <a href="https://en.wikipedia.org/wiki/de:Lexikon_der_gesamten_Technik" class="extiw" title="w:de:Lexikon der gesamten Technik">w:de:Lexikon der gesamten Technik</a>), <a rel="nofollow" class="external text" href="http://ctgpublishing.com/sir-william-arrol-biography/living-model-principle-of-the-forth-bridge-1890/">Maybe 1890</a>
<a rel="nofollow" class="external free" href="http://www.sbe.hw.ac.uk/staff/arthur/frbpc/ForthBridgePostCards.htm">http://www.sbe.hw.ac.uk/staff/arthur/frbpc/ForthBridgePostCards.htm</a>