What you have is a large gas bubble that broke and corroded. The coin is badly corroded could have been a ground coin or just left in the street and got like that from the enviorment. JC
In 1982 around October, everything changed when the U.S. Mint started striking cents with a core 99.2% comprised of zinc and .8% copper, with the cent bearing a thin outer coating of pure copper. In fact, the entire coin had become almost entirely made from zinc, 97.5% zinc to be precise. Copper now comprised just 2.5% of the total metal content in the new Lincoln cents. The copper cent weighs 3.11 grams, whereas the zinc cent weighs 2.5 grams.
