First binocular microscope of the Optische Werke Ernst Leitz.
Unknown author<span style="display: none;">Unknown author</span>
<a href="https://de.wikipedia.org/wiki/Felix_Jentzsch" class="extiw" title="de:Felix Jentzsch">Felix Jentzsch</a> (1914): <a rel="nofollow" class="external text" href="https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2818.1914.tb01727.x">The Binocular Microscope</a>, p.5