Ron Guth:
The 1870-S Dime is a semi-scarce issue, in sharp contrast to just about every other denomination issued in San Francisco in 1870 (for example, the 1870-S Half Dime and Three-Dollar Gold piece are unique and the 1870-S Silver dollar is exceedingly rare). The San Francisco Mint produced 50,000 Dimes, virtually all of which entered circulation. A small quantity was preserved by collectors such that perhaps 20-30 Mint State examples are known today. Most of the known Mint State examples are well-preserved, usually in MS64 to MS65. The best examples are MS66, but only several are known in that grade.
The strike on the 1870-S Dime is often soft in the centers, particularly on the N of ONE and the IM of DIME.