Key dates for U.S. Wheat Pennies:
Date and Approximate Mintage
 
1909-S - 1.8 million
1909-S VDB - 0.5 million
1914-D - 1.2 million
1922 (No mint mark) - unknown (D is missing)
1931-S - 0.9 million

 

Key dates for Mercury Dimes:

 

The key dates in the Mercury Dime series are as follows:1916-D - With a mintage of only 264,000 this is by far the rarest Mercury key

  • 1942/1 (2 over 1 date) - Overdate type for both 1942 and 1942-D, mintages are unknown but the type is extremely rare.
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Semi-key (scarce) dates in the Mercury Dime series include:

  • 1921
  • 1921-D
  • 1926-S
  • 1931-S
  • 1931-S