Have you a silver dollar, or a gold piece? Your papa has. Perhaps you never noticed that coins are cut in regular up and down grooves around the edges. This is called "milling," because it is done in the government money mill, or mint. Coins have been milled for so long a time by all countries, that no one knows just when the practice was begun. But the reason for it is very well known. Dishonest people used to shave away thin layers from the edges of coins. When the edges were smooth this could be done, and no one could detect the theft unless the coins were weighed. When the edge is grooved or milled, stealing in that way is not so easy. New grooves, as regularly spaced and as evenly cut, could not be made again, except by melting and re-minting the coin. Copper pennies and nickels are not milled, for the metal in them is not valuable enough to pay any one for the trouble of shaving the edges away.