I dunno - it kind of looks like the die subsided near the rim. You can see the curvature in IGWT, and the coin is decidedly anomalous at the junction between rim and field.
Well, don't take my opinions as Gospel. I'm not one for "conventional wisdom," and feel like there is complacency in numismatics - a willingness to settle for the opinions of experts rather than think for oneself - which causes misinformation. This one is too "cute" to just immediately settle on grease as the cause. Grease doesn't make the fields of a die curve, as we see at the top of this coin. And whatever affected the die did so around the entire circumference, as shown by the dark stripe around it.
Between the dark stripe, missing digits/letters and the odd halo around the bottom left shoulder of Lincoln I wasn't sure how to classify this coin.