Picked while coin hunting through rolls of pennies for wheats, pre-1981s, and Canadians. Tossed into reject bag, but landed face down. The zinc that's exposed has tarnished slightly since I first found it, but still appears fresh and clean having been inside of a cardboard flip for the last 4+ years. Is this a mint error? If so, is it valuable? the missing copper layer also affects the edge on that section of the coin.
Your coin was struck on a defective planchet. It may be worth a $1 or 2 to someone that wanted it. It has exposed zinc that some folk shy away from.
As long as it doesn't get damp, the zinc won't rot away. Always a risk with zlincolns (and another reason why common errors are less valuable after 1982).