Some physical characteristics of money include durability, portability, divisibility and an inability to be counterfeited or duplicated. Coins are typically made from refined metals, such as gold, copper or nickel, and paper currency is manufactured to ensure bills can remain physically intact for many decades.
Paper currency was first developed and used by the Tang Dynasty in seventh century China. Earlier forms of currency were based on the trade of precious metals. Paper currencies were initially seen as a promissory note that would later be redeemed with payment upon presentation, but these notes gradually led to removal of precious metals from most monetary systems.