The Seated Liberty Silver Dollar series officially concluded in 1873, and there is no record of a regular-issue Seated Liberty Silver Dollar dated 1870-S.
The "S" mintmark typically denotes coins minted at the San Francisco Mint, and it wasn't until later in the 19th century that the San Francisco Mint started producing silver dollars.
Numismatics is a field that occasionally sees discoveries or private minting efforts that may not be widely documented.
It's also possible that there might be confusion with other denominations or coins, so it's recommended to have the coin examined by an expert to ensure accurate identification and authentication.
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The Seated Liberty Silver Dollar series, spanning from 1840 to 1873, is known for its elegant design featuring Liberty seated on a rock, holding a shield and an olive branch.
During this period, the San Francisco Mint (mintmark "S") primarily focused on minting smaller denominations, and the production of silver dollars in San Francisco became more prominent in the later 1870s.