I'd have to produce my proofs book, but my first impression is that it's not a ball and shot gun

No sights, raised rib, and it looks quite light

We've seen French, Belgian, and Austrian guns with straight rifled chokes that were so outfitted for management of the wadding, and/or to act as spreader chokes for rapid pattern evolution

I wouldn't be betting that this gun was built with single projectiles in mind