Ron Guth: The Jefferson Nickel replaced the Buffalo Nickel mid-1938. The original design ran from 1938 to 2003, although war-time "Nickels" of a special silver alloy are treated as a different type. PCGS breaks the original design into Vintage (1938-1964) and Modern (1965-2003) types; this distinction is purely arbitrary (1964 was the last year that silver coins were produced for circulation in America but this, of course, has nothing to do with the non-silver Nickels).
All of the date/mintmark combinations in this series are common, although there are many strike- and condition-rarities. Strike-rarities are those with Full Steps; condition-rarities are those with exceptionally high grades. Many collectors focus on the separation of the steps leading up to Monticello as the standard for a fully struck coin. Thus, the premiums paid for Full Step Nickels are often substantial compared to softly struck examples. Some of the greatest Full Step rarities stem from the 1950s and 1960s, when quality control at the Mints seems to have been at its lowest. Condition-rarities arise from the hardness of the nickel alloys used on these coins and the general carelessness with which they were handled during the minting process.
The 1950-D Nickel garnered lots of publicity in the 1960s, when roll collecting was at its peak. While not a particularly rare, or even scarce, coin, the 1950-D attracted many collectors and speculators because it had the lowest mintage of the series. Even today, the 1950-D is remembered as the "toughest" date in the series, but there are many coins that are worth considerably more in high grades, with Full Steps, or a combination of the two.