I cant see any lines or other features that would indicate an insert on the bit but the eye has definitely been formed by wrapping a piece of steel around a mandrel and I would imagine that a piece of tool steel would then have been inserted between the two ends of the steel that forms the eye.
Having another look there is a fault about halfway between the edge of the bit and the eye which may indicate an insert. I'll get a photo in the morning light. It is hard to see any detail because the surface is rather pitted. Since it is a double bevel axe this does not concern me but it does obscure any features that would otherwise be visible.
