Weird- not sure of the ignition system- internal hammer attached to the outside hammer perhaps striking the central stud thing in the rear of the breech-block. If the nipple, it has been smashed shut by dry-firing.
Interesting mould that casts small round projectile with grooves matching the barrel's rifling already on the projectile.
It appears to 'take' a very small charge.
Well made "piece" that would not be inexpensive.