Picked up my latest mint purchase, the 2019 silver proof set with bonus reverse proof penny. Unfortunately it looks as though these too have the weird discoloration like the first proof penny. The darker tone on the reverse proof penny I just received is at the bottom of the bust of Lincoln on the mirrored surface. The reverse looks fine.
I only have a phone camera but this close up of the lower bust displays the mottled discoloration. Can be seen best when tilting the coin.
I received my proof set today. The "storage" envelope for the cent was in the box, but the cent was not. I called the Mint. They will send me the cent...
@Joshua Lemons. If it were mine I'd return it and ask for a replacement. You may have to return the whole set. Call the US Mint to find out.