That coin is 1806/5 T-1/O.104b, a late die state of the first half dollar die marriage struck in 1806. It is the only half dollar overdate from a previously used obverse die, that was used on two different DM's in 1805. It did not last long in 1806. The reverse die was also used in 1805 - four different DM's! The late reverse die state has two cuds: The OP half dollar that Bryce5 posted is also interesting, the 1806 T-24/O.118a with a shattered reverse die and a die chip in OF.