The bracelet-like manilla was a horseshoe-shaped rod with flared ends. Most were composed of copper or brass, although there are rare examples made of gold. Manillas were the first true currency of West Africa and were used from the late 15th Century to the mid 20th Century.
There were several different varieties of manilla. The various peoples of West Africa valued each kind differently and were selective regarding the kinds that were acceptable to them in trade. Interestingly, the value of a manilla was determined, in part, by the quality of the ringing sound it made when struck.
Europeans used manillas in their trade with West Africa and large quantities of them were actually produced in Europe for this purpose. Infamously, manillas became a major form of currency in the slave trade and, thus, they are sometimes referred to as "slave trade money."
Manillas are similar to other bracelet-like currencies that have been used in Africa. Those other forms are distinguished, however, in that they are wearable as adornment.