Half Cents:
1793-1795.....Pure Copper / 6.74 grams
1795-1857.....Pure Copper / 5.44 grams

Large Cents:
1793-1795.....Pure Copper / 13.48 grams
1795-1857.....Pure Copper / 10.89 grams

Small Cents:
1856-1864.....88% Copper, 12% Nickel / 4.67 grams (Copper-Nickel)
1864-1942.....95% Copper, 5% Tin & Zinc / 3.11 grams (Bronze)
1943.............Steel coated with Zinc / 2.70 grams (Steel)
1943.............Bronze, 95% Copper, 5% Tin & Zinc / 3.11 grams (Extremely rare coin, 40 specimens known to exist.)
1944-1946.....95% Copper, 5% Zinc / 3.11 grams (Recycled Cartridge Cases)
1947-1962.....95% Copper, 5% Tin & Zinc / 3.11 grams
1962-1982.....95% Copper, 5% Zinc / 3.11 grams
1974.............96% Aluminum with trace metals mixed in (possibly Tin and Zinc) Extremely rare but some do exist / .937 grams (5-14 coins believed missing Philidelphia mint, 10-12 from Denver mint.)

1982-Date......99.2% Zinc, .8% Copper core with a plating of pure Copper with a total content of 97.5% Zinc, 2.5% Copper / 2.5 grams

2009.....Bicentennial Lincoln satin-finish collector set has 95% Copper, 5% Tin & Zinc / 2.5 grams