I would like to know your initial thoughts about it ? What lead you to think it may be something special? Plus full images of front and rear.
best guess I know how a pressroom works and its not just work work work. philly is known for errors I live here. there. found in a roll with cob webs so no tarnish
All US Mints are known for errors. You just need to tell the difference between a damaged coin and true mint errors.