Magnificent!
Agree with Ariel, but my guess would be 19 century rather than early 20.
Daghestan but also possibly Georgia.
Can you take a close-up photo of the maker's mark?
As Ariel suggested, maybe Rivkin's book on arms and armour of the Caucasus can give you more hints.
PS: Love the fullering and the niello! Fantastic piece and in great condition.