CONGO (DEMOCRATIC REPUBLIC): iron knife (423g), 23.5cm-long blade on a 16cm-long wooden handle, made by the Mangbetu people of northeastern DR Congo, VF, ex Charles Opitz Collection. Opitz divides African metal currencies into 3 rough catergories based on their utility. The first category includes objects where the distinction between their use as tools and use as money is minor. The second category includes those that retain their original shape, but are made of a finer, perhaps less practical material. Objects in the last category have completely lost their shape as practical tools and instead have a standardized weight and size, and are therefore strictly a currency. As metal was a scarce commodity in Africa before the 20th century, all three categories were considered extremely valuable and widely used in exchanges.
Estimate: $200-250