What is the value of an 1858 US half dime?

Look on the back of the coin to see if there's a small mint mark letter. It may be blank or there may be an O.

Numismedia lists the following approximate retail values as of 09/2010:

No mint mark (Philadelphia):

Very worn condition - $14

Moderately worn - $20

Slightly worn - $24

Almost no wear - $102

Uncirculated - $156 to $9,380 depending on quality

No mint mark, inverted overdate:

Very worn - $36

Moderately worn - $63

Slightly worn - $144

Almost no wear - $356

Uncirculated - $600 to $5,220

"O" mint mark (New Orleans):

Very worn - $14

Moderately worn - $22

Slightly worn - $35

Almost no wear - $154

Uncirculated - $222 to $2,410

DISCLAIMER: The values quoted are the best available, but may vary due to market fluctuations. Also the wholesale (buying) price of a coin will be less than the selling (retail) price. A reputable coin dealer will be able to give a more accurate valuation based on inspection of the coin.