In 1982, the US mint switched from a copper cent to a copper plated zinc core. This decision created four varieties: copper and zinc from both the Philadelphia and Denver mints. Four varieties of any date is rare but the 1982 cent became exceptional when large and small date varieties were discovered in both the Philadelphia copper and zinc cents and the Denver zinc cent for a total of seven varieties. No small date varieties in the Denver copper cent have been identified, yet.
Three decisions are required to correctly identify a 1982 Lincoln Cent variety. The first and easiest step is to identify the mint: Cents from Philadelphia have no mint mark and those from Denver feature a D below the date. Next, compare the date to this large date variety courtesy of The Coin Page
Determining the composition is the most difficult step. If you have a scale capable of measuring to tenths of grams, the copper cent weighs approximately 3.11 grams and the zinc cent weighs 2.5 grams. While the scale is the most accurate method, the zinc and copper cents sound different when dropped. The copper cent has nice ring tone compared to the thud of the zinc cent.