A key date for this issue is the 1921.  A low mintage makes it scarce today.
Adolph A. Weinman never intended his design for the obverse of the new dime introduced in 1916 to represent Mercury but that of Liberty, her winged cap symbolizing "liberty of thought," not fleetness of foot. Minted in 90% silver, the mintage of 1.2 miliion is only greater than that of the most sought after 16D and the 21D which had a marginally smaller mintage.
An affordable G4 addition to a type set or hole in an album.