Metallic money may circulate by weight or by count. In its earliest form it circulated by weight, but the practice was very inconvenient. So long as money circulated by weight, there was no misapprehension as to the nature of money - it was a commodity exchanged in kind for other commodities, and the barter nature of the operation was clearly evident. To introduce circulation by count, it was necessary for an authoritative person or institution to issue pieces of the metal uniform in size, content, and design, and attest to this uniformity by the imprint of his or its stamp. Such pieces had to be so designed as to maintain their full weight. When they were so designed, any reduction by erosion, sweating, clipping, and the like, being easily detected, would render their acceptance improbable except by weight. The act of manufacturing uniform coins and stamping them in some way as a guaranty of their purity and of their weight is termed coinage. The confidence of the commercial public in these coins is much greater if the general government does the coining, although there is no reason why a private coiner cannot coin as competently. The state's duty of enforcing contracts and imposing penalties, and the requirements of revenue, caused the state to safeguard the manufacture of a sound and reliable medium of payment. Coinage has therefore become a state monopoly, and the legislative body defines the name, weight, purity, and metal of the different coins; and in order to maintain the public confidence in these coins, it proscribes all private coinage and prosecutes counterfeiting. Quite the world over, coinage is vested in the state.