In 1875, the Philadelphia Mint experimented with two different mintmark placements for the branch mints at San Francisco and Carson City. One version has the mintmark placed normally, below the wreath. On the "odd" version,. the mintmark is placed within the wreath in the field below the word DIME. The reason for the experiment is unknown, and may just be a misplacement of the mintmark by an employee unfamiliar with the history of the series.
Mintage figures do not break out for the two different types, but the PCGS Population Report shows that the "Mintmark Below" 1875-CC Dime is about three times as rare as the "Mintmark Within".
PCGS has certified over 30 Mint State examples of the 1875-CC Mintmark Below Dime, with the majority of the coins distributed fairly evenly among the MS62-65 grades. The finest example is a single PCGS MS66.