This 10-heller brown stamp was issued in 1917 for Bosnia & Herzegovina under Austro-Hungarian administration, featuring a finely engraved portrait of Emperor Karl I. Part of the K.u.K. Militärpost series, it was used by military postal services during the final years of World War I. The design displays intricate side-panel ornamentation and the country name BOSNIEN-HERCEGOVINA prominently across the top, typical of the late imperial period.
Collectors value this issue for its historical context—Karl I’s short reign and the collapse of the empire give this series notable significance. Postally used examples, such as yours, highlight authentic wartime circulation.