A series of dimes bearing the face of Franklin Roosevelt but missing a mint mark released in 1982 by the U.S. Mint in Philadelphia could be worth thousands of dollars each, writes Robert Higgs for ...

Here are some key takeaways: Most U.S. coins sport a mint mark — a P for the Philadelphia Mint, S for the San Francisco Mint, D for the Denver Mint, or W for the West Point Mint. According to ...