From 1864 to 1982 all cents weighed 3.11 grams whether they were bronze or copper, with the exception of the wartime steels, which weighed 2.7 grams.
You may have an experimental piece on your hands, or a bad scale possibly? Recheck the weight with a different set of scales, then think about sending it to a gradings service for verifying it. Possibly a little nickel was added?