Rawhide Mounted Plains Indian Axe/Club

When my grandfather passed away a couple of years ago we cleaned out his house and my father saved some of his collected Indian things. Now I'm selling some of the stuff since my father is out of a job currently. A friend has told me that this is a club or axe mounted to a wooden stick with rawhide. It is a wicked looking thing. It is 21 1/2" long not counting the loop at the end of the handle. It has sort of a knob at the end to help you hold it. He does not know what tribe may have made it but thinks it probably was from the plains. Don't know where or when my grandfather got it. I kind of like it, so I'm sellling it with a reserve of $120.