Watch List notes:

PAPUA NEW GUINEA: ndap shell money (15.58g), Opitz p.236 (plate example), ca. 46 x 50mm, used exclusively by men on Rossel Island (Yela), VF, R, ex Charles Opitz Collection. Culturally and linguistically distinct from their Austronesian neighbors, the people of Rossel Island boast one of the most complicated monetary systems in the world. There are two kinds of shell money in use, ndap and kê (as well as secondary valuables such as greenstone axes). Ndap are single flat shells of polished Spondylus and are known as men's money, while nko are strings of ten discs made from Chama shell and known as women's money. The former come in 22 different grades, with the high-ranking ones usually smaller and worn to a delicate shape and patina through generations of handling. Those pieces are known by individual names to the islanders, who treated them with religious reverence and reserved them for specific purposes. For instance, number 18 is used in payment for wives, while a number 20 was used as compensation for ritual murder. The higher pieces are loaned, rather than traded, and paid back with interest, sometimes over the span of several years. It has been called a form of prestige currency and is not directly comparable to Western monetary systems.

Estimate: 250-300 USD