Notice that Liberty's hairlines, especially above her ear, are not as prominent on your coin as they are on other Mint State Peace dollars. This is common on 1921 coins because the hair oftentimes did not strike up all that well because of the high relief. It should not be mistaken for wear. (Compare yours to the MS62 1934D that Santinidollar posted just below yours where the hairlines above the ear are much more prominent.)