Anyone see History Channel where they showed the finding of the ship "Capitana" off the coast of Equador? They were pulling up Bronze cast cannon balls, which had a dual purpose in those days. 1) Cannon balls..(duh!) and 2) barter or trade for the precious metal, ie: copper, used in the bronze. If they didn't need to fire them at an enemy, they traded or sold them for other goods or services. Thought that was pretty smart of them in the day!