There are a lot more multi-millionaires in America today than possessors of this rare numismatic treasure. Complete date and mint collections are extremely difficult to assemble in any numbers. A leading Walking Liberty specialist has stated, "The difficulty of finding certain key dates in circulated grades is just about mind-boggling."
The key no-mintmark 1921 Philadelphia and 1921-D Denver issues had original mintages of just 246,000 and 208,000 respectively. Those were the lowest U.S. circulation coin mintages of the past nine decades. They're well below the key 1928 Philadelphia Peace dollar's mintage of 360,649 and less than one-tenth of the lowest Franklin half dollar mintage of 2.5 million.
Other key scarcities include the 1916 Philadelphia, 1916-D Denver, 1916-S San Francisco, 1917-D Type I, 1917-D Type II, 1917-S Type I, 1919, 1919-D, 1921-S and 1938-D issues.