There is no way to say without knowing the age, type, size and condition of the coin. I would check the library for a good coin guide, or a trustworthy coin dealer.
In order to really know the value of the coin, you need to know the exact type, quality, size, metallic content, etc of the coin. If you don't know this info, visit a coin dealer/appraiser to help you out.
It can be quite difficult to just guess at the value of a coin. Is the coin circulated or uncirculated, what condition is it in, what's the year, is it worn on the high spots? Without seeing the coin there is no real way to put a value on it.
