found this many years ago as a kid and just now crossed paths with it again. Found coin roll hunting.
It looks like a die cap. They usually have multiple strikes on one side and the other side looks normal or close to normal.
Looks like there was a very thin die cap that fell off of the obverse die and got struck into this coin. Where the cap included the letters of LIBERTY the added thickness there got impressed into this coin, leaving you with one raised LIBERTY and one incused LIBERTY. There would be similar indentations elsewhere. Very nice error!