No, there is no "M" mintmark for use on US Coins. There was however from 1920-1940 an "M" mintmark for the Manila branch of the US mint, they however made no coins intended for circulation in the US but rather coins for the United States' territories.
In addition, two famous US coins carried an "M" as their designers' monograms: the Morgan dollar, designed by George Morgan, and the Standing Liberty quarter, designed by H. A. MacNeil.
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The U.S. has 4 Mints that make coins. The Philadelphia & Denver Mints make the coins we use every day. Primarily, the San Francisco Mint makes Proof coins and the West Point Mint makes gold, silver and platinum bullion coins.