This is what they call the "mumps" version or anomoly in certain dates of barber half dollars. http://blog.davidlawrence.com/index.php/barber-halves-chapter-4-year-mint-mark-analysis-1907-o/
MUMPS – Refers to coins which exhibit a goiter-like swelling on the neck and jaw of Liberty. Found on quite a few dates from 1901 to 1909. Mostly but not exclusively on O-mints. Usually not noticeable on coins below VF grade. Appears to have been caused by some sort of die buckling. (Also seen on Barber Quarters of the same period) Edit: From the Glossary of the David Lawrence book.