Vikings sold cheap copies of their sword called the Ulfberht.
Their original Ulfberht was made from steel imported from the
Middle East. Apparently they found a market for their swords and
made copies from cheaper metal and sold them across northern
Europe, where archaeologists would find them around a millennium
later. Today the swords are described as having been too soft
and as having buckled or broken easily when used in battle. 21st
century researchers say that by the 11th century, after the
Russians blocked access to the Volga River, it became almost
impossible for the Vikings to obtain the higher-quality steel
that they used in making their swords.