There are several groups of Maidu. The Mountain Maidu  were the only one of these groups that produced all black designs on white (also known as Northeastern Maidu), The stitches on the outside of the tray (the nonworking surface) are split. Both of these characteristics, along with the leftward direction of the weave (seen on the inside of the tray or the working surface) and the materials that were used help identify this tray as Mountain Maidu. (Kania and Blaugrund, Antique Native American Basketry of Western North America: A Comprehensive Guide to Identification {Marquand Books, Seattle, 2014), p. 187-188.

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