The 1931-S Lincoln cent holds an interesting place in the canon of wheat pennies, serving as the least expensive of the key dates and priciest of the semi-keys in the series. Many consider this coin to be a "key," while others categorize it as a "semi-key." Regardless, it holds the unequivocal title as the second-lowest mintage of all regular-issue business strikes in the series with only 866,000 made, behind only the 1909-S VDB penny and its anemic mintage of 484,000.
Like the 1909-S VDB Lincoln cent, the 1931-S was saved in huge quantities upon its release because collectors knew at the time this Depression-era coin had a low mintage. The coin was saved in roll and even bag quantities, some of which were appearing on the market as recently as the early 1980s. As this coin was kept in pristine condition by so many collectors for the duration of its existence, the coin is about as common in circulated condition as it is in uncirculated grades.
This situation also helps to explain the tight price spread between circulated pieces and typical uncirculated specimens. The coin ordinarily sells for about $65 and up, with AU50 specimens trading for around $100 and BUs fetching approximately $150 or higher. Red gems grading MS66 are rare and usually command prices above $1,000. While the 1931-S Lincoln cent is considered quite scarce and is in high demand by collectors, it's available for a price and can be found with relative ease in the marketplace.
Image is courtesy of Heritage Auctions, www.HA.com.