The only two known 1975 No S dimes are currently worth approximately $400,000 each. These coins, made especially for collectors, were issued in U.S. Mint proof sets. In addition, these coins have a mirrored finish not to be confused with 1975 Philadelphia minted dimes found in pocket change that have no mint mark. It should be easy to tell the difference.
You can always call and ask Bob. There are yearly books that come out and explain the current value of coins in retail.
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