Wasco-Wishram Sally Bag

A Wasco-Wishram Sally Bag. I am a bit unfamiliar with this type of basket due to their rarity. This appears to be woven in hemp or horsehair or even a combination of both. Extremely tight and very flexible. I had a collector comment that it may have been made by the Nez Perce. Any comments welcome. Stands 6 1/2″ tall and approximately 7 ” in diameter.