It has been in my collection of Native Americans relics for about 15 years. The feather indicates a "coup" (act of bravery in warfare), with a notch meaning an enemy killed with scalp taken as a war trophy.
A piece of US history. See size (expressed in centimeters). The item "Very Scarce Antique Centenary Native American (Sioux) Tomahawk Indian Wars" is in sale since Saturday, June 9, 2018. This item is in the category "Collectibles\Cultures & Ethnicities\Native American\ US\1800-1934\Other Nat.The seller is "blackops--1" and is located in Châteauneuf le Rouge. This item can be shipped worldwide.