Vintage Mexican Aztec Mayan Tribal Face Copper

This is a vintage, one of a kind Mexican tribal face necklace. Love the expression on the face, it has character. The face seems to be made of some sort of clay or carved out? The rest of the necklace seems to be made out of copper or brass. The copper has not been polished and has the original old patina. The only mark is Mexico with a crown hallmark above the word. Unique and one of a kind!