In 1870, employees at the San Francisco Mint produced over one million Half Dollars. This was larger than the Half Dollar production at the Philadelphia and Carson City Mints combined. Nonetheless, because of the great distance between the San Francisco Mint and collectors back East, very few 1870-S Half Dollars ended up in collections. This is best illustrated by comparing the 1870-S with the 1871, which has a slightly larger mintage than the 1870-S. However, far more Uncirculated examples of the 1871 have survived compared with the 1870-S. This large discrepancy can be attributed to the presence of far more collectors surrounding the Philadelphia Mint.
Less than two dozen Mint State 1870-S Half Dollars exist. Most grade MS62. Gems are extremely rare and none are known above MS65.