Please check your coin again and post a new, separate question. No half dimes were minted at San Francisco until 1863.
$30-$50 depending on condition. http://www.pcgs.com/prices/PriceGuideDetail.aspx?MS=1&PR=1&c=121&title=Liberty+Seated+Half+Dollar
The value of a 1842 seated liberty dime is about $20 in G-4(good) condition.
Arrows at date S.L. halves were struck at the New Orleans Mint for 9 years, a DATE would help. Post new question.
It is a counterfeit.
349
Anywear from $28 and up
$13 in good condition
$20-$1,300
There are only 4 known genuine 1861 C.S.A. Seated Liberty half dollars. Many replicas and counterfeits exist.
A date is needed, post new question.
Retail price range is $15.00-$25.00 for coins with heavy wear medium wear is $50.00-$150.00 and light wear is $220.00-$330.00 a mint state coin starts at $480.00
Well its about 100-200$ if it is in good condition.