My first impression of the gun, and the same impression I get right now, is that it is a cheap trade gun made for the African market and very much like the ones shown in my Stoeger 1949 catalog reprint. Doubles with carved stocks, strap brass guard, superficial engraving and cheap locks. The one I have leaning in the corner is stamped Spain on the top of the breech. I know nothing of the barrel grooves but imagine them simply decoration easily machine accomlished.

As for the Pauly, here is a photo I shot of the one belonging to Daryl's and my close friend. I did some rather delicate restoration on the gun and wrote a story about it for an early issue of Shooting Sportsman.

(This photo looks little odd because it is a scan of two magazine pages)
The Pauly had a stock carving remotely similar, but vastly more complcated than the gun presented here. They may hve been done on the same continent, but that would be the only commonality to this double in question.
Best,
Steve