The rivet is copper ore.

The copper theme is repeated in this ceremonial rattle in the shape of that esteemed object. The face has been shaped by pounding into a rounded bulge, and a similarly rounded piece of copper has been soldered to the back, forming a cavity that holds a number of small stones, or perhaps lead shot. The characteristic T-shaped ridge appears on the lower section. (Holm, Crooked Beak of Heaven, 1972)

Coppers vary widely in size, but this one seems too small for actual use as a copper. It may have been made for some decorative use. The fact that this copper is made of brass weighs against its use as a real copper. A face is painted on the upper, flaring section, and there are stripes and stars on the two sides of the lower part. (Holm, Crooked Beak of Heaven, 1972)

The rivet is copper.

Great ladles, with figures of mythical creatueres carved on their handles, are used to distribute food from the feast dishes. The Burke Museum collection includes a pair of large ladles decorated with carved Sisioohl heads. The Sisioohl head is conceived as an extension of the handle, bent back upon itself and joined to the neck of the spoon. The head, with its coiled nostril, scaly crest, and spiral horn, is deeply carved and painted in black, red, green, and white. (Holm, Crooked Beak of Heaven, 1972)

One of the most characteristic objects of Northwest Coast manufacture is the copper. Superficially resembling a shield, it had throughout the northern coast a place of high regard as an object of chiefly paraphernalia. Among most of the coastal people, and especially among the Kwakwaka'wakw, it was considered to represent monetary wealth. (Holm, Crooked Beak of Heaven, 1972)