While Lincoln wheat cents are generally regarded as a common series and still appear occasionally in circulation, they are nonetheless an obsolete series that does boast some real key and semi-key dates. Perhaps the most notable of these is the 1909-S VDB cent, which is the lowest-mintage regular-issue issue in the series. Some 484,000 were struck, and it is estimated that perhaps 20,000 survive. While the 1909-S VDB is not necessarily a rare coin in the absolute sense, it is one of the most well-known scare coins around and is famous well beyond numismatic circles. Other scarce regular-issue entries in the Lincoln wheat series include the 1911-S, 1914-D, 1924-D, and 1931-S. Among the rare varieties are the 1922 no-D, 1943 bronze, and 1944 steel cent. Meanwhile, the 1955 doubled die is widely considered the most popular of all United States die varieties and enjoys perennially solid demand.