I believe that coins minted from 1944 to 1981 contain 95% copper and weigh 3.11 grams. According to 31 U.S. Code § 5113 - Tolerances and testing of coins states "...The weight of the one-cent coin may vary not more than 0.13 gram"... therefore anywhere from 2.98 to 3.24 grams is normal weight. Also note that wear and damage may cause additional weight variance.