Die Deterioration effect. As you get closer to the rim the Die is deteriorated more.. This is just my theory.
He is... http://www.fredweinberg.com/ He is also a consulting Editor for this website... http://www.error-ref.com/ And a member of CoinTalk
Oh my. You should measure them. Fred is our expert in letter shapes and sizes and that would definitely be important for him to know. Do you have a ruler?