What this coin looks like (obverse, reverse, mint mark location, special features, etc.): One major variety is the 1900-O/CC Morgan Silver Dollar. This coin features a New Orleans "O" mintmark struck over a Carson City "CC" mint mark - which resulted in parts of the underlying "CC" being visible around the "O" on the reverse of the coin. These features are depicted by the arrows in the example closeup image below:
At first it seems bizarre how a Carson City "CC" mintmark could even appear on this coin considering the fact that the Carson City Mint stopped producing dollar coins in 1893 - 7 years earlier. The Philadelphia Mint is responsible for producing the coin dies before shipping them out to the branch Mints. One theory is that since Carson City was no longer producing Morgan dollars - The Philadelphia Mint simply took the old dies and partially defaced the "CC" mint mark and replaced it with the "O" mint mark before sending them to the New Orleans Mint. Another theory is that the engraver accidently punched the "CC" mintmark onto the coin and later replaced it once the mistake was found.
Coin valuation chart: Typical coin prices, values and worth per grade or condition - in USD