The key dates for the U.S. Wheat Pennies are as follows:
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
From Susan Headley, former About.com Guide
This 1914-D Wheat Ears Penny is a key date cent in average circulated condition.
Photo courtesy of Harlan J. Berk, Ltd.The key dates for the U.S. Wheat Pennies are as follows:
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