How can you tell that the copper was chemically removed? Were there any 1983 pennies released that werent copper plated ?
I'll post it again - If it's dark, dull and grey, it's been de-plated (like the OP's coin) If it's bright and shiny, it's been re-plated. Genuine Cents struck on unplated zinc planchets are very scarce, and must have the right 'look' and luster. Genuine examples exist since they were first struck, but very very few have been made/released in the past 15-20 years.
1983 Lincoln Cent is Zinc component and coin contained 97.5 % zinc. So , we have left only 2.5 % for very tinny copper. Somebody removed tinny copper by acid. Accident , nothing else.