Yua currency shell ring, Maprik area, East Sepik Province, Papua New Guinea. Tridacna shell. 6.5" (16.5 cm) diameter. Late 19th to early 20th century. From the giant tridacna clam shell, currency rings were laboriously crafted with grit, water and bamboo, and used as bride price over generations. This “yua” is tapered at both interior and exterior edges and has a lot of character on its surface.