Rarity of numismatic objects
There have been several rarity scales developed for coin collecting, such as R1 through R5, or �R� for rare and �RRRR� for extremely rare. None have become a rule of thumb in numismatics. The rarity scale created by J. Hewitt Judd decades ago: R8 = 1-3 known �Unique or Nearly Unique� R7 = 4-12 known, �Extremely Rare R6 = 13-30 known, �Very Rare� R5 = 31-75 known, "Rare" R4 = 76-200 known, �Very Scarce� R3 = 201-500 known, �Scarce� R2 = 501-1250 known, �Uncommon� R1 = more than 1251 known, �Common� Rarity numbers come from educated guesses and participant experience. With slabs came grade-rarity, the second method of ranking a coin, and with that much price manipulation.
Source: Numiscadero Spanish to English Glossary (Gary Beals)