Key date

In coin collecting, a key date refers to 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.

For example, the 1909-S VDB is the key date in the Lincoln cent series. The 1914-D and 1931-S are considered semi-keys. In the United Kingdom £1 coins from 1988 are considered key date coins.

What makes a coin a "key" is somewhat more complicated because there are many issues that are easy to obtain in lower grades and very hard to find in higher ones. Collectors who want a series in near uncirculated condition may find some date/mint combinations extremely rare. This is because low mintage coins were frequently kept by collectors and saw little or no circulation, while common dates were rarely saved and typically became heavily worn. Another factor in making these conditional rarieties is that in certain years some or all of the mints did poor strikings of a coin. For example, finding the common 1919-D Walking Liberty half dollar in well struck, near-perfect uncirculated condition, is an almost impossible challenge for even the collector of substantial means.

Professional and avid coin collectors will often not simply collect coins, but will specialize on a specific types of coin and then attempt to collect every coin in the series, i.e. one from every year that type of coin was minted with all variations, most notably mint mark, but can also be material; the coin was minted out of (some years, the same coin might be made out of two or even three different metal combinations, such as steel, nickel, iron, gold, bronze or silver) and even artistic differences or errors on the die that struck the coins and at the highest quality that can be found.

Often, locating a "key date" coin for a set is what stands between a complete set and just a collection. Once completed the entire set's value increases significantly.

Partial List of Key Date U.S. Coins

• 1877 Indian Head Indian Head Cent
• 1909-S Indian Head Cent
• 1909-S VDB Lincoln Cent
• 1909-S Lincoln Cent
• 1914-D Lincoln Cent
• 1885 Liberty Nickel
• 1886 Liberty Nickel
• 1912-S Liberty Nickel
• 1913-S Type II Buffalo Nickel
• 1916-D Mercury Dime
• 1921-D Mercury Dime
• 1916 Standing Liberty Quarter
• 1932-D Washington Quarter
• 1932-S Washington Quarter
• 1916-S Walking Liberty Half Dollar
• 1921-D Walking Liberty Half Dollar
• 1893-S Morgan Dollar
• 1895 Morgan Dollar (known only in proof)
• 1921 Peace Dollar
• 1928 Peace Dollar