1866 ($3,000/12,500), 1867 ($2,500/12,500) and 1873 open 3 ($2,500/12,500) are equally the next most difficult dates to find in full red.
1866 PCGS MS66RD
1871 PCGS MS66RD
   1871 ($4,000/15,000) actually has a slightly lower mintage than 1872 and ranks third in value.