Common, scarce and rare U.S. coins at Mintmark.com; also links to bullion and mechanical coin banks.
"COINS OF THE UNITED STATES DOLLAR—United States coinage was first minted by the new republic in 1792. New coins have been produced every year since then and they make up a valuable aspect of the United States currency system. Today circulating coins exist in denominations: $0.01, $0.05, $0.10, $0.25, $0.50, and $1.00. Also minted are bullion (q.v., Silver Eagles) and commemorative coins. All of these are produced by the United States Mint. The coins are then sold to Federal Reserve Banks which in turn are responsible for putting coins into circulation and withdrawing them as demanded by the country's economy.
Current coinage—Today four mints operate in the United States producing billions of coins each year. The main mint is the Philadelphia Mint, which produces circulating coinage, mint sets and some commemorative coins. The Denver Mint also produces circulating coinage, mint sets and commemoratives. The San Francisco Mint produces regular and silver proof coinage, and produced circulating coinage until the 1970s. The West Point Mint produces bullion coinage (including proofs). Philadelphia and Denver produce the dies used at all of the mints. The proof and mint sets are manufactured each year and contain examples of all of the year's circulating coins.
The producing mint of each coin may be easily identified, as most coins bear a mint mark (also spelled mintmark). The identifying letter of the mint can be found on the front side (obverse) of most coins, and is often placed near the year. Unmarked coins are issued by the Philadelphia Mint. Among marked coins, Philadelphia coins bear a letter P, Denver coins bear a letter D, San Francisco coins bear a letter S, New Orleans (previous links to New Orleans Mint at Wikipedia) coins bear a letter O and West Point coins bear a letter W. S and W coins are rarely, if ever, found in general circulation, although S coins bearing dates prior to the mid-1970s are in circulation. CC and D mint marks were used for a short time in the early-to-mid-nineteenth century by temporary mints in Carson City (previous links to Carson City Mint at Wikipedia), Nevada and Dahlonega (previous links to Dahlonega Mint at Wikipedia), Georgia, respectively; all such coins are now in the hands of collectors and museums . . .
Remarks (1-8)—1. The mass and composition of the cent changed to the current copper plated zinc core in 1982. Both types were minted in 1982 with no distinguishing mark. Cents minted in 1943 were struck on planchets punched from zinc-coated steel which left the resulting edges uncoated. This caused many of these coins to rust. These steel pennies are not likely to be found in circulation today, as they were later intentionally removed from circulation for destruction.
2. The Wheat Ears Reverse cent was mainstream during its time. Some dates are rare, but some can still be found in circulation.
3. Nickels produced from mid-1942 through 1945 were manufactured from 56% copper, 35% silver and 9% manganese. This allowed the saved nickel metal to be shifted to industrial production of military supplies during World War II.
4. Prior to 1965 and passage of the Coinage Act of 1965, the composition of the dime, quarter, half-dollar and dollar coins was 90% silver and 10% copper. The half-dollar (also called a halve; halves plural) continued to be minted in a 40% silver-clad composition between 1965 and 1970. Dimes and quarters from before 1965 and half-dollars from before 1971 are generally not in circulation due to being removed for their silver content.
5. In 1975 and 1976 Bicentennial coinage was minted. Regardless of date of coining, each coin bears the dual date 1776-1976. Quarters, half dollars and dollar coins were issued in the copper 91.67% nickel 8.33% composition for general circulation and the government-issued 6-coin Proof Set. A special 3-coin set of 40% silver coins were also issued by the U.S. Mint in both Uncirculated and Proof.
6. For coins, use of Kennedy half dollars, Susan B. Anthony dollars (also called SBA dollars) and Sacagawea dollars is not as widespread as that of other coins in general circulation; most Americans use quarters, dimes, nickels and cents (also called pennies) only. Coins are minted for general release through banks and other financial institutions, and are also available for collectors in uncirculated rolls, mint sets and proof sets from the United States Mint.
7. The Presidential Dollar series features portraits of all deceased U.S. Presidents with four coin designs issued each year in the order of the president's inauguration date. These coins began circulating on 15 February 2007.
8. The Susan B. Anthony dollar coin was minted from 1979-1981 and 1999. The 1999 minting was in response to Treasury supplies of the dollar becoming depleted and the inability to accelerate the minting of the Sacagawea dollars by a year. 1981 Anthony dollars can sometimes be found in circulation from proof sets that were broken open, but these dollars were not minted with the intent that they circulate.
Bullion coins—Non-circulating bullion coins have been produced each year since 1986. They can be found in silver, gold and also platinum since 1997. The face value of these coins is legal as tender, but does not actually reflect the value of the precious metal contained therein. On 11 May 2011, Utah became the first state to accept these coins as the value of the precious metal in common transactions. The Utah State Treasurer assigns a numerical precious metal value to these coins each week based on the spot metal prices . . ." — Coins of the United States dollar at Wikipedia