* http://en.wikipedia.org/wiki/Standing_Liberty_QuarterEarly Standing Liberty quarters had the date too high and so it quickly wore off, although chemical treatment can sometimes bring back the numbers. For the collector this creates particular problems for the two rare issues of the series, the 1916 and the 1918/7-S. While the 1917 Type One issue is quite common, the previous year there was a very low mintage of only 52,000. Although some of these early pieces were quickly saved from circulation, this was not the case with the overstruck date issued two years later. In higher grades this is one of the most expensive circulating U.S. coins of the 20th century. In 1925 the date was recessed into the step, allowing the coin rim to protect it from wear. Evidently this modification did cause the dates to withstand circulation better, since pre-1925 dates fetch prices many times higher than post-1925 dates, even given roughly equal mintage numbers in the same state of preservation.