This is a California winnowing basket. There are several tribes that are in the area and this could fall under any of them. However, it may be a Washoe basket because of the weave, shape and material. This basket has willow shoots that have been split and the dark weave might be dyed. This is used to sift after gathering seeds, berries, clean water, etc. It is in excellent shape and has no breaks. A unique piece to add to your collection.