cannonmn,
I would think that maybe it was used as a test fixture for his percussion lock system. It seems that there were quite a few holes that were placed in the breech area then filled. There seems to be a bit of scaring on the rim behind the vent. Maybe, from a lanyard? or, someone dragging it.
Well, that my un-educated guess. It's a nice piece and I would like the know the history as well. The markings is what makes it real interesting.