Certification of a piece of metal or other material (such as leather or porcelain) by a mark or marks upon it as being of a specific intrinsic or exchange value. Croesus (r. c. 560–546 BC) is generally credited with issuing the first official government coinage of certified purity and weight. Counterfeiting was widespread in the Middle Ages. In the late 15th century, equipment capable of providing coins of reliable weight and size was developed in Italy. The Industrial Revolution saw further refinements in coinage techniques. Most of the basic motifs of modern coinage were introduced in antiquity. In the Greek world, relief imprinting gradually replaced the roughly impressed reverse punch of the Lydians. Alexander the Great introduced the coin-portrait; these initially depicted gods or heroes and later living monarchs. Until the end of the 19th century, Chinese coins were cast much like those of the early Greeks; the square-holed Chinese bronze coins were issued in essentially the same size and shape for almost 2,500 years.