Cents actually haven't been copper since 1857. Starting in late 1864 they were made of Bronze, 95% copper 5% tin and zinc. There were temporary changes during WWII, then back to bronze. In 1962 the tin was dropped making them brass,95% copper 5% zinc, then in 1982 they were completely changed to the present copper coated zinc. So your coin would be made of brass. No way it could have been struck that thin, the acid affects the surfaces pretty evenly leaving the image as the coin erodes. Pretty interesting find nonetheless.