Unofficial Bulgarian war-time National and War flag, used only during military operations between 1879 and 1945. In fact it represents reversed Bulgarian National flag. (According to Voynikov, Ivan  "Part II. The Bulgarian flag through the centuries" in  (in bulgarian)   History of the Bulgarian State Symbols. Archived from the original on 26 June 2017. Retrieved on 29 December 2012. , retrieved on September 20, 2007).
Own work, vectorized from File:Unofficial Bulgarian War-time flag.png
Original PNG by Dimitar Navorski, rewritten in SVG by Ricordisamoa