1837 was the debut year for the new Seated Liberty Dime. The first Dimes of the year bore a so-called "Large Date", a curious, transitional date with a serif on the top bar of the 3 and a flat-topped 7. Later in the year, a "Small Date" was introduced which became the standard size and style for the next several years. The Small Date variety has a round-top 3 that distinguishes it from the flat-topped 3.
According to Breen, "Large date 1837's were saved as first of their kind" but the same was not true of the Small Dates. Breen's statement is corroborated by the PCGS Population Report, which shows a population for the 1837 Small Date at nearly a fourth of that of the 1837 Large Date. Mint State examples of the Small Date are scarce and usually appear in grades from MS62 to MS64, inclusive. Gems are very rare. The best example is the single PCGS MS66+ illustrated above.