A "clear" S mintmark is one where the "S" is very distinguishable. The "filled" S mintmark is one where the "S" is more blob like (it looks more like an 8 than an S)
A coin with an S mintmark means is was made at the San Fracisco Mint.
Look on the back below the DO in DOLLAR. It could be black or there could be a small O, S, or CC mintmark. Value as of June 2012: No mintmark:$52 "O" mintmark:$156 "S" mintmark:$52 "CC" mintmark:$540
You just spend it. Unless you have a coin in a mint-set with an "S" mintmark that is either proof or uncirculated, your coin is worth $1.
A morgan silver dollar cost minimum 30 dollars but if it has a "S" or a "CC" mintmark it can sell up to 130 dollars.
1923 Peace Dollars are so common circulated coins with no mintmark sell for 16.00-$20.00. Coins with a D mintmark are $16.00-$28.00 and the S is $16.00-$24.00. The actual value depends on the grade of the coin.
While 1910 is not a rare date for Barber dimes, it is silver, so at a minimum it has a current silver value of about a dollar. You also need to check the back, near the bottom, for a mintmark. There may be a "D" or an "S" there. With full rims on both sides, and an "S" mintmark, it's worth about $3.00 If all the letters of LIBERTY on the headband are readable, then with no mintmark it's worth $2, with a "D" mintmark it's worth $6, or with an "S" mintmark it's worth $35 If all the details are strong, with only a slight amount of visible wear, then with no mintmark it's worth $15, with a "D" mintmark it's worth $35, or with an "S" mintmark it's worth $80 If your coin is a nice uncirculated example, then with no mintmark it's worth $75, with a "D" mintmark it's worth $150, or with an "S" mintmark it's worth $300
The mintmark will be on the reverse of the coin under the wreath. The mintmark will either be a D or S or may have no mintmark, in the case of a coin with no mintmark it was minted in Philadelphia.
For a Lincoln cent, any mintmark is under the date on the obverse. Indian Head cents have the mintmark on the reverse under the wreath and can only be an "S" mintmark, on just on the 1908 & 1909 issues.
If it is a "s" quarter it will always have the S mintmark. You can find this mintmark usually on the back of the coin. The exact location will depend on the type of quarter.
Most of the time the silver quarter is part of a set and is rarely seen alone. It isn't really a rare coin and would sell for about $2 for silver scrap. Keep in mind though that most quarters dated 1976 are NOT silver and the only silver quarters made in 1976 are 40% silver and all have an "S" mintmark. However, the San Fransisco mint made copper-nickel quarters with an "S" mintmark also, so having an "S" mintmark does not mean the coin is silver, but a coin without an "S" mintmark is for sure not a silver 1976 quarter.
It's simple. A 1922 S silver dollar will have a S mintmark while a 1922 D silver ill have a D mintmark. The mintmark is located on the reserve below the word "ONE".