What Makes a Coin a "Key Date"?

Defining Key Dates

A "key date" is a coin whose date and mint mark combination is significantly scarcer and more valuable than other dates in the same series. Key dates are the coins that make or break a complete collection — and the ones that can turn a junk box find into a windfall.

What Creates a Key Date

• Low mintage — Fewer coins struck means fewer available. The 1916-D Mercury dime (264,000 minted) vs the 1945 Mercury dime (159 million) illustrates the extreme range.
• Low survival rate — Many coins were melted, lost, or destroyed. The 1893-S Morgan dollar had 100,000 minted but very few survived in high grades.
• Hoarding — Sometimes low-mintage coins were saved in quantity (1950-D Jefferson nickel), making them common in uncirculated but scarce in circulated grades.
• Demand — Collector demand drives prices. Popular series like Morgan dollars have more key date demand than less-collected series.

Key vs Semi-Key vs Common

• Key date — The scarcest, most expensive date(s) in a series. Usually 1-3 coins. Example: 1893-S Morgan, 1916-D Mercury dime.
• Semi-key — Moderately scarce dates that carry premiums but are obtainable. Example: 1921 Walking Liberty half.
• Common date — Readily available at modest prices. The backbone of most collections.

Condition Rarity

Some coins are common in low grades but rare in high grades. The 1884-S Morgan dollar is available for $30 in VF but exceeds $10,000 in MS-65. These "condition rarities" offer opportunities for collectors who can spot undergraded coins at coin shows.

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