What this coin looks like (obverse, reverse, mint mark location, special features, etc.): The 1942 42 over 41 Overdate Error (1942/1-D) was one of the major errors in the silver Mercury Dime series. This error from the Denver Mint is also very noticeable but not as much as the same error that came from the Philadelphia Mint. This is best identified by noticing the 1942 date punched over a 1941 date. The underlying "1" is slightly noticeable as blobs near the top and bottom of the "2" and part of the doubled "4" is seen near the bottom of the "4" as depicted by the arrows in the example image above.
Coin value chart: Typical coin prices, values and worth in USD based on grade/condition