Yes Braunschweig is it (see the Immota Fides phrase), perhaps officers shako from the "Herzoglich Braunschweigisches Infanterieregiment Nr.92" (before 1886)? In that year the military convention with Prussia took place and they received a change in uniforms and insignia. Also the term "Herzoglich" was removed from the regiment's name. I am not sure though if all battalions carried the same headdress. In 1867 the former Leib-Bataillon became the third battalion so there might have been a mixture right until 1912 when all battalions received the scull.