Zarma Copper Mondua Currency

Four inches across, heavy, and made to be seen on the wrist. Across West Africa, a ring like this was a way to wear your wealth and store it at once.

This is a mondua, a copper bracelet from Nigeria, dating to the 20th century. It is an open, C-shaped band of solid metal that ends in two large, bulbous terminals. The outer curve is closely ribbed with fine, parallel grooves, giving it a coiled look. The knobbed ends are smooth, with light pitting. The copper has mellowed to warm reddish brown, darker in places, with the soft sheen of long handling.

An account book you could wear. Tidy, really.