Ron Guth: The 1870 Three-Cent Silver has the second lowest mintage of any date in this series (second only to the extra-rare 1872). One might conclude from this fact that the 1870 is also the second rarest date in terms of the number of survivors, but there is no such correlation between the mintage and the level of survivorship. Rather, the 1870 is similar to the higher-mintage 1865, but the latter has far more Mint State examples in the census. Either way, the 1870 is a tough date and one which will present a roadblock for the collector seeking a nice example.
The typical Mint State example is only MS64. Gems are scarce and become virtually impossible to find above MS66 (in fact, PCGS has certified only a single MS67 -- and none finer).
The overal strike characteristics of most 1870 Three-Cent Silvers is good, and clashmarks are seldom an issue. Certification is recommended to ensure the difference between a rare Mint State and the more common Proofs.