The 1842 FS-301 Half Dollar is a particular repunched date with strong doubling at the base of the 8 and 4. Less visible is the doubling at the base of the 2. This variety commands a 20% premium over the normal 1842 Medium Date Half Dollar.
High grade examples are very elusive. The finest example appears to be the NGC MS65 from the Eric P. Newman Education Society collection (ex Col. E.H.R. Green).