David Hall: Due to the fact that it has the third highest mintage of any of the 1916 to 1939 Walking Liberty half dollars, the 1918-S is one of the most common Walkers in lower grades. I remember that as a kid in the late 1950's and early 1960's, the one pre-1934 Walker you could find in change was the 1918-S. However, the 1918-S is scarce in mint state and one of the rarest Walkers of all in Gem MS65 or better condition. This date obviously wasn't saved in any quantity at the time of issue. In fact, the 1918-S is rarer in Gem condition than all other Walkers except the 1919-D, 1921-S, and 1918-D. It is about equal in rarity to the 1917-D reverse, 1917-S obverse, and 1921-D, all key dates in the Walking Liberty half dollar series. For mint state examples of the 1918-S, strike can be a problem. Well struck examples are definitely very rare. Luster is usually a more subdued satin white, or the coin can have toning of varying degrees.
Gerald R. Forsythe Collection