Hi Cerjak.
First of all, congratulations. That is definately one of the more interesting long guns I've seen. It's beautiful, interesting, and curious all at the same time. LOL.
I'm going to say it is Moroccan (likely), or possibly Algerian. The lock looks like locally made, copied from the English pattern of Snaphaunce. It would be worth removing the lock to see if there are any marks on back of the lock plate.
The camel bone inlay and circle decoration definately looks Moroccan. While the trigger looks Algerian. But as Kubur mentions, the trigger guard looks some what Sardinian, but shorter, and a bit wider.
But as you point out, the really unique feature is the Western/European style butt stock. It would be interesting to know how THICK the butt stock is? Is it thin? Or is it closer to 2" thick, similar to European guns ?
Unlike many of the guns that were made for general re-sale, I believe this gun was made exactly to a customer's specifications. The stock reminds me of the Bulgarian style long guns, made in the Balkans, with the stock decorated with pearl panels over most of the stock. But your's with a definate Moroccan design and lock.
A super interesting gun. And a beauty!!!! Would sure look good in my gun room. LOL
Rick.