Certainly looks like Orrefors. I seem to remember a thread some time ago about a vase with a bird on it that was held to be Orrefors despite the absence of a signature on the bottom. The point being that Orrefors can occasionally be unsigned. However, I don't think it would greatly change the intrinsic or extrinsic value of the vase if it turned out to be by Kosta, for example.
David