Elsinox It looks to be a black powder pistol.
Powder would be put in the barrel then a round ball pushed into it.
The protrusion on the barrel with the hole is called a nipple.
A percussion cap would be placed on that.
The hammer (long piece that pivots) would be released to impact the cap.
It should have spring tension that sends it toward the barrel.
The percussion cap will ignite the black powder through the little hole in the nipple.
I cannot see a trigger mechanism but the hammer would be squeezed towards where the blade pivots and released somehow or manually.
Very cool and in really good shape.
