During the Great Depression, the Mill denomination reappeared in the United States. Quite a few states changed their sales tax rates to include mills. That is, instead of 4 percent, it might be 4.3 percent. Taxes were expanded to include lower priced items like gum and candy, but the fractional cent amounts could not be collected without a corresponding coin. The federal government did not issue such a coin, so the individual states had their own "coins" made. In Missouri, we had 1 and 5 mill tokens to pay the tax. The first were made of cardboard! Then they changed to zinc and later to plastic. In Missouri the mills were still being used in the 1950's; I think they finally went out of use in 1961. I just bought an amusement park ticket of the 1930's or 1940's which had the admission price and the tax worked out to three places. Since these tax tokens were authorized by the state and circulated as and with regular money, they could be considered coins. As far as I know, the only prices in the USA still expressed in mill amounts are for gasoline. I suspect other items have taxes worked out to mill amounts, but the tax is rounded off.