I will go along with Austrian or German military but not with the kammerbuchse. The kammer portion refers to a sort of chamber where the snail and nipple of a normal percussion gun would be. There is a spring much like a frizzen spring to keep the top of the chamber closed and the hammer appears to strike down on the top of the chamber which ignited either a tube type primer or perhaps percussion powder/ pellets. I didn't read far enough to go into the details of ignition only looked at the photos on the net. I can't see any sign of a outside spring or chamber top in the original photo
cheers mooncoon