The 1921 Missouri was struck to commemorate the 100th anniversary of Missouri statehood. A very large mintage was authorized but many were melted as unsold. There is some comtroversy as to the actual "distributed" mintage and even experts disagree. To add to the confusion, there are two varieties of the Missouri and the exact mintage breakdown between the two is speculative. The two varieities are one with a 2 and a 4 struck into the obverse field with a star between the 2 and the 4. In numismatic circles, this variety is known as the "Missouri 2 by 4". The other variety does not have the 2*4 in the field and is known as the "Missouri plain". The 2 and 4 were meant to signify that Missouri was the 24th state admitted to the Union and the idea was to have the 2 by 4s sell for a premium to defray the cost of production. But as it turned out, both varieties were sold at an original price of $1.00. The distributed mintage for the plain Missuri has been reported as between 10,428 and 15,428 coins. The Missouri 2*4 mintage has long been listed at 5,000 coins. However, there is a problem with the 5,000 figure for the Missouri 2*4 in that it is just barely rarer than the the Plain Missouri. My personal feeling is that the 15,428 figure is too high and the 5,000 is too low.
Whatever the true distributed mintage, the two Missouris are among the rarest issues in the silver commemorative series. For the Plain Missouri, the typical grade can range between AU50 to MS64. MS65 specimens are somewhat rare and Superb Gem MS66 examples are truly rare. Marks are usually not a problem with this issue. Strike can be somewhat of an problem, but the real issues with Missouris is eye appeal. Frosty, full luster Gems are much rarer than dull or toned examples. Many Missouris have varying degrees of toning, some natural, some otherwise. But many of the toned Missouris are quite dark. Serious collectors should hold out for a frosty white Gem or an attractive, naturally toned piece.