To clear things up:
- It's a buffalo, not a bull. A bull is the animal used in bullfights in Mexico and Spain.
- F is the initial of the coin's designer, not a mint mark. The mint mark, if there is one, is on the back under the Words FIVE CENTS.
- The coins called Liberty nickels were minted for circulation from 1883 to 1912. Even though your coin has the Word LIBERTY on it, it's called an Indian Head or Buffalo nickel.
Assuming that its date is in fact 1913, please see the Related Question for more information about values and design varieties.
