Strange - standard Euro choke, then a jug choke with a long end-choke (long parallel section before muzzle).
This is roughly the jug choke I lapped into the bore of my .44 smoothrifle. The choked part was 3" long along the horizontal and about .005 to .006" deep only. There was 3/4" between the muzzle and the end of the choke, (hense the term - probably English, "End Choke".
The gun still shot round ball extremely well for having no rifling, yet patterned 1/2ounce of shot well enough to win a trap shoot breaking 10 straight at rendezvous against everyone else using double 12's and a 10 bore. This was before the flood of 20 bore French guns arrival and those people with smothbores, had Navy Arms and Dixie doubles & used them for ducks and geese with lead shot.