Looks like a die chip on the U in United. The heads side looks like environmental problems...could have been in the ground ? Wait for more opinions...
Looks to have a couple of die chips. Common for a 50' wheat cent. The discoloring on the obverse would allow me to return it to circulation.
Thank You for waking me up to the fact the coin has no rare value because of die chips on one the reverse..and the condition of coin is too damaged to be of any value to any collector