[barrysloate]

The coin rarity rating is not really adjectival but in common usage a numerical one. Coins are rated from Rarity 1, the most common, to rarity 8, which approaches unique.

For example, a T206 Wagner, assuming 60-75 are known, would be a R5-.

A T206 Plank, assuming 100+ known, would rate a R4.

A Cobb with Cobb back, of which there are roughly 13, would be a 6+.

And a Doyle Nat'l, with 8 known, would be a R7.

The coin hobby, which has been around a little longer than ours, has a very good knowledge of how many of every date and variety are known. All the great rarities have been well documented. As more research and data accumulation is done with vintage baseball cards, the more likely a similar rarity scale will be implemented.