Who knows,, it could have been an (artist) painters attempt to engrave or etch the same scene. No telling at this point who did it I guess.
I wonder about the loading gate screw. I appears to have been left in place while the work was done and worked into the pattern as a handy flower center. None of the other screw heads or tips are so done.
Perhaps it was stuck in place on the old rifle. 'Hell with it,,make it a flower'
The scroll work itself isn't very well laid out for what there is of it. It's not something an accomplished engraver would turn out. It has it's moments but for the most part it doesn't begin to flow as any sort of scroll work should. The lines are the wrong thicknesses and in wrong positions. Just arbitrary fillers in many cases w/some leaves added here and there.