This is a massive and ancient tridacna clam shell currency ring from the Kubalia area of the Prince Alexander Mountains, Papua New Guinea. Called "head rings" these super thick examples would have been at the head of the line when laid out on the ground during a bride price transaction. All the smaller and lesser rings would have been lined up below this head ring. This one is an excellent example with significant age-there are over 52 use marks cut into the inner ring. Thus this ring has been through at least 52 bride price exchanges over many generations. The piece has beautiful shell "grain" and a great glossy patina. The ring is 10 ¾" in diameter and nearly 2" thick. It is 19th century or earlier and priced at $4500. Questions?