The list of rarest Capped Bust dime varieties are as follows.  As you can see, 1820 JR-12 is around the 3rd or 4th rarest Capped Bust dime die marriage.  The present example grades VF-35 by PCGS, and sits around #6 or 7 in the condition census.  Color and condition are choice and original.  Nicer examples seldom show up for sale, especially in public auctions, thus this is a rare opportunity to acquire a rare and high-condition census variety!
 
1) 1827 JR-14 (2 known)
2) 1827 JR-10 (~16-20 known)
3) 1820 JR-12 (40-50 known)
4) 1833 JR-3 (40-50 known)
5) 1824/2 JR-2 (45-55 known)
6) 1829 JR-10, curl base 2 (50-60 known)