Help with ID

[Shooting Centre]

Anyone have any ideas what this rifle is? Calibre is about 15mm, bore is rifled. There is a small Belgian proof on the barrel but nothing else.

 

[camerl2009]

well its a muzzleloader

about .58-.60 cal in inchs

other then that idk

 

[wr.sainsbury]

i.d. help

unusual bolster-looks austrian circa 1850's. the back action lock makes it this age or later. no ramrod?