Please post a new question with the coin's date.
There can't be a 1966-S nickel because the Mint didn't use any mint marks from 1965 to 1967.
If your coin has a "S" mint mark on it means that it was made at the San Francisco mint in California.
If the mint mark is a D the nickel is probably worth no more than a dollar. If the mint mark is an S it could be worth around $3.00 By the way, there is no such thing as a 1938 liberty nickel. The only nickels minted in 1938 were buffaloes and Jeffersons.
5 cents.
If it was found it pocket change spend it
It depends on the type. There were two types: silver-clad and a copper-nickel-clad. Silver-clad contains 0.14792 ounces of pure silver. All have an S mint mark. Copper-nickel-clad does not contain any silver. They can have a D, S, or no mint mark.
If circulated condition its worth about 25 cents if ok quality. If it has a d mint mark about 4.00. If S mint mark about 2.00. If un circulated double all the prices
Unless it's uncirculated, 5 cents. Nickels from Philadelphia did not carry a P mint mark until 1980. FWIW, San Francisco did not strike any coins for circulation between 1956 and 1967 inclusive, so a 1959-S nickel would not be possible.
With no mint mark under the words FIVE CENTS: $1 if very worn, $4 with moderate wear. With a D mint mark, $8-30 With an S, $4-25
On a 1962 nickel, the mint mark is located on the reverse side of the coin, to the right of the building depicted in the center. It can either be a "D" for Denver or an "S" for San Francisco, depending on where the coin was minted. If there is no mint mark, it was minted in Philadelphia.
The S mint on this and any U.S. coin means it was struck in San Francisco. The link below shows all mints and their letter marks.
about $1,945