The 1891-CC FS-501 $10 gold piece is a nice, clear example of a repunched mintamrk. The first mintmark was punched further to the right of the final placement. The most obvious remnant of the original mintmark is a curving arc coming out of the base of the second C. This arc can be seen even on low grade examples.
As interesting as this variety might be, it commnds little or no premium over the price of a regular example of this date. Several Mint State examples are known, the best of which are a couple at the MS64 level. This is a variety that can still be cherry-picked today.