A difficult to find date of an otherwise fairly easy series. Examples are the 1946 and 1949 Threepences and most of the 1905 silver coins. Click here to see the British key date coins from 1821 - 1970.
a coin whose date and mint mark are extremely scarce and therefore much sought-after by collectors
Low mintage / rare coins in a coin series normally the most expensive ie: 1909 S VBD Lincoln cent. L mint mark - only found on the 1864 Indian cent. Stands for Longacre the designer.
a scarce date required to complete a collection, usually more difficult to find and afford.
Among the scarcest (and therefore most expensive) members of a coin series, e.g. the 1909-S VDB Lincoln cent or 1916-D Mercury dime
a scarce date usually required to complete a coin collection
Key Dates refer to a coin that is the very rarest coins in a series and therefore the most expensive coins. Key Dates even in low grades are very valuable and highly sought after.
a scarce date that is often hard to find to complete a collection.
Slang usually indicating the rarest (and therefore most expensive) date-and-mint of a particular coin series.
An extremely low mintage and /or certified population, which results in higher collector interest. Nearly every coins series has one or two issues with such dates. For example, the 1916-D in the Mercury dime series or the 1911-D in the $2-1/2 Indian series.
Used in coin collecting; a key date is a date (or date and mint mark combination) of a given coin series or set that is harder to obtain than other dates in the series. The next level of difficult to obtain coins in series are often referred to as semi-key dates or simply semi-keys.