Katanga Cross and Slave Manillas

Now, while these pieces aren't exactly "coins" per se, they were both used as currency. I purchased these pieces from an estate and they will become part of my permanent collection. 
Both pieces originate from Africa during colonial times. The Katanga Cross was a form of currency used in the Congo region of central Africa during the mid-19th century. They measure roughly 8 inches across and weigh roughly 800 grams (1.75 lb.). As currency, a Katanga cross would buy about 10 kilograms (22 lb.) of flour, five or six fowls, or six axes. Ten would buy a gun. They were cast in sand molds pictured below.

The two bracelets in the first photo are known as Manillas and were used as currency during the slave trade. These bronze or copper pieces were produced in England, typically Birmingham, and brought to the coast of west Africa for trade. A typical Manilla of roughly 3" would have enough value to purchase a single slave from an indigenous tribal leader. Larger or more decorative pieces than the ones shown here carried an even higher value. These Manillas are a grim reminder of one of the darkest eras of western history.