An early pneumatic from the Ukraine which I think may be a valve operated gun as the trigger controls a slide to the rear end of the gun. This is a speargun in the gunsmith tradition as exemplified by the pistol-like grip handle. The only drawback in this gun is the low handle position with respect to the spear propulsion axis as the gun is then more susceptible to muzzle flip. The absence of a hand pump and a rear inlet valve cap indicates that this is a gun that pumps up via the inner barrel which is quite common for releasing valve guns from that part of the world. With that solid looking handle the gun is most likely a sinker after the shot.
The gun seems to have no muzzle relief ports as the ring of machined cutouts are probably there to lighten the nose cone and allow a point of purchase to twist the nose cone during gun assembly. As releasing valve guns are usually held together by the outer tank the end bulkheads screw in to the tank ends via screw threads which would be consistent with the observed proportions of the gun.
If there are radially directed holes in the base of those nose cone cutouts then they are unusual to be placed there as more metal to drill through to reach the inner barrel. However relief ports need to be rearward of the anvil face, hence the length of the shock absorber anvil in the muzzle needs to be considered.