The first answer is hard to improve on, so don't expect mine to top that one. The boring answer is that the San Francisco mint made a mistake in 1970, stamping-out 2,200 proof dimes with the wrong die. All dimes minted in San Francisco are supposed to have the letter 'S' stamped on them. read more
Technically, it’s only the 1970 “No-S” Proof Roosevelt Dimes that are particularly valuable. If you have an ordinary 1970 dime, it’s value depends on its condition. If it’s worn the way you might expect of a coin that’s been in circulation for 47 years, it’s worth 10 cents. read more
So when we say average, we mean in a similar condition to other coins issued in 1970, and mint state meaning it is certified MS+ by one of the top coin grading companies. Additional Info: These are pretty generic run of the mill 1970 Franklin D. Roosevelt dimes. read more
Many of the most valuable dimes on this are from the early 19th century which was a time when the dime, like the United States Monetary System, was very young. The dime was the first coin made by the United States Mint, starting in 1796. read more