Most muzzle loaders were cylinder bored thus not apt to find the
NON POUR BALLE stamp regardless of when made. Firing ball was a common practise & the NON POUR BALLE mark came in practise as choke boring became common in breech loaders. With a muzzle loader if the ball could be loaded through the muzzle it could be fired, thus little need for the mark on a ML'er. A solid ball could be fired safely through a choked breech loader if a size of ball was selected which would pass through the choke but a bore size ball was apt to "Lift the Choke".
