Understanding Key Dates and Rarities
In order to understand what key dates and rarities are, you must first know the difference between a condition rarity and a true rarity. Below I will try and explain;
True Rarity – Based on three main components,
1. Survival – how many examples are known to have survived since their minting
2. Mintage – how many coins were struck or created
3. Series Length – how many years was the coin made
Condition rarity – This can be the total number of extant specimens or the number of examples in a particular grade and higher. Typically condition rarities have a high survival rate or mintage (or both).
Key Dates, True Rarity & Condition Rarity
The rarest or most important coin in a series is called the “key” coin. It is usually the lowest-mintage coin with the lowest survival rate and/or the most desirable coin in that particular series.
A good example of a key date is the 1911-D $ 2.5 Gold Indian, for instance, is considered the key coin of the $ 2.5 Indian series. It is the lowest mintage coin of the series and the most desirable. It is also the most expensive in any grade but has far outperformed the other 14 dates in the series. The terms “key to the set” or “key to the series” are also used as synonyms for “key coin.”
A good example of a true rarity is the 1794 Flowing Hair Silver Dollar – approximately 100-150 coins survived this year from the original 1758 that were minted. The Flowing Hair series ran for only two years 1794 & 1795
An good example of a condition rarity is the 1924-P Saint Gaudens in Mint State 68 – PCGS has currently graded only 1 coin in this condition but has certified more than 261,000 in all grades. This date also has a mintage of over 4 million coins and the series ran from 1907-1933 with 53 different dates, mintmarks and varieties.