Where is the Mint Mark on the American Eagle Silver Dollar?

By GovMint :

The mint mark on select American Silver Eagles can be found on the coin's reverse (tails) side, just below the eagle's tail feathers. A mint mark only appears on Proof, Burnished, and other collector versions of Silver Eagles, like Reverse Proofs. Mint marks do not appear on bullion Brilliant Uncirculated (BU) versions. However, it is still sometimes possible to tell which branch of the United States Mint struck such issues thanks to identifying serial numbers on sealed monster boxes.  

The mint mark indicates where the coin was produced, with "W" representing the West Point Mint and "S" for the San Francisco Mint. Identifying the mint mark on American Silver Eagles is essential for collectors and numismatists to determine their origin and potential collector appeal.

Sources Used:

https://www.usmint.gov/coins/coin-medal-programs/american-eagle/silver-proof