This is a gravity-fed reserve Fuel Tank - and a piece of the propellor hub - from an LVG C.II of Feldflieger-Abteilung Nr. 61 that was shot down on 12 March 1916 over the Bois de Thiescourt by Georges Guynemer of Escadrille N.3. The entire story is told in the article La 8e Avion Boche de Guynemer from the Winter 2018 issue, Issue No. 4, of Over The Front, the Journal of the League of World War One Aviation Historians.