Heavy Bulgarian siege gun during the <a href="https://en.wikipedia.org/wiki/Siege_of_Adrianople_(1912-13)" class="extiw" title="w:Siege of Adrianople (1912-13)">Siege of Adrianople</a>
G. Woltz (active 1900s-1910s)
<a rel="nofollow" class="external text" href="http://www.gutenberg.org/ebooks/37760"><i>L'Illustration</i>, No. 3652, 22 Février 1913</a>