I think you will find the Chassepot is converted to the 11mm Gras cartridge.cartridge.
https://en.wikipedia.org/wiki/Chassepot
" Nearly all rifles of the older Chassepot model (Mle 1866) remaining in store were eventually converted to take the 11 mm Gras metallic cartridge ammunition (fusil Modèle 1866/74). About 665,327[4][10] Chassepot rifles had been captured by the German coalition that defeated France in 1871. Large numbers of these captured Chassepot rifles were shortened and converted to 11 mm Mauser metallic cartridge. It served with cavalry units of the Kingdom of Saxony and of the Kingdom of Bavaria.[11] Others were disposed of "as is" with British surplus dealers. In most but not all cases, the French receiver markings on these German-captured Chassepot rifles had been erased."
Details of the German conversions can be found in;
“The German Rifle, A comprehensive illustrated history of the standard bolt-action designs,
1871-1945”. By John Walter. Includes information on the use of captured French Chassepots