very interesting double rifle made between 1864 and 1867 , SN 5733 https://www.kunst-waffenkammer.de/newsletter_artikel/seltene-zuendnadeldoppelbuechse/?lang=de

the unloading rod is missing

muzzles showing the typical view we knowing from military rifles

and the lands/grooves are given with 15,1-15,2mm /16.1-16,2mm so its clear the common military bullet with paper sabot was loaded into the 0,71" Schlussspiegel cartridge