Spirally twisted copper was the original currency of the Ibo, and then the cowrie shell was introduced in the 16th century. Similar, I suppose, to the gold sovereign being supplanted by bits of paper. When cowries were rare, a few could buy a woman, but as supply increased the price went up to twenty bags-full. It was women’s councils among the Ibo that set the cowrie exchange rate, and one suspects that the inflation must have had something to do with the women’s own evaluation of themselves. But in times of inflation gold becomes king, and similarly, while cowries devalued, a bar of copper like this could be relied on to stock a considerable harem.