Rarity Scale
Estimate of the surviving population of a coin.
Unique: One known
R-8: Estimated two or three known (Excessively Rare)
R-7: (High) Estimated four to six know (Extremely Rare)
R-7: (Low) Estimated six to 12 known (Very Rare)
R-6: Estimated 13 to 30 known (Rare)
R-5: Estimated 31 to 75 known
R-4: Estimated 76 to 200 known
R-3: Estimated 201 to 500 known
R-2: Estimated 501 to 1,250 known
R-1: Estimated over 1,250 known