@JBJ
The spout stopper, spout, and butt plug are all hard maple in this case. As you asked, your question is the same as I had as well. From the pictures I've seen there are bone, horn, and wood spouts, but I haven't seen reference to which was most common. I chose the hard maple for the aspect of the wood, and it's what I had readily available. Hope some of the real horners give an answer.
As a side note: The shape of the pour spout is not exactly similar to the Lancaster horns I've seen. I may take another crack at it and try too get the shape more closely matched to the "school", since changing it for another is relatively easy.