Ron Guth: Production of Half Dimes ended in 1873. The government's goal, since 1866, was to replace the silver Half Dime with a nickel five cent piece. By 1873, the endeavor was considered a success and the tiny Half Dime was retired forever. Despite the official preference for the new "Nickels", the mintage of Half Dimes remained high at Philadelphia in 1873 (higher than many dates in the 1960's and 1870's.
As a result, this date can be found with relative ease in all grades, up to and including MS-64. In higher grades, the 1873 Half Dime becomes scarce. The finest example certified by PCGS as of August 2011 is a single MS-67.