This is certainly different, probably only it's maker knew what it was for! Looks to me like it was forged from a double faced sledge. I think that some kind of adze could be close to the mark, but I can't yet conceive what for? On the bay it would be called a "blacksmith's hammer", but I'm sure it's not a blacksmith tool, at least I've seen nothing like it (yet)!?. Thanks HeelSpur for challenging us.
Graeme
PS When I first saw the side view, I thought of that forester's tool called a pickeroon? That's not how it is spelt but was that what you were thinking of HeelSpur?
G