I realize the "Not For Ball" marking on English guns is a sign of a very old gun. The French language version of that marking, "Non Pour La Balle" over "choke" meaning the exact same thing it meant in England, is still in common use on French guns to this day, so, rest assured, I have a good grasp of what it actually means.

That mark appears in the upper left on this French gun, a modern 28 gauge of all things. It makes me wonder, didn't these guys ever hear of the lowly 30-30 caliber rifle cartridge, which, would surely be superior to loading pumpkin balls into a 28 gauge birdgun for larger game?
Weird, huh?
What I don't have a good grasp of, is, why anyone would look at internet pictures of this gun and think that what round balls they could use and why was an issue they needed to resolve right away, or why they would not think of an implement better suited to that task, and maybe move on to other issues, that seem just a bit more pressing, to me, anyway, involving any future use of this gun.
Just as an aside, based on what you have seen in the photos, how would you proceed with this gun, based on a slim entry price, and your own wallet sponsoring the bill for suitable restoration?
I can state, without any doubt at all, I don't know of anyone using round ball loads out of a shotgun, circa 2015.
Thanks for the history lesson.
Best,
Ted