A three-legged buffalo nickel in circulation is worth anywhere from $400 to $1,000, while one that is not in circulation can pull in $20,000 or more. The condition of the coin is important to collectors, so the ones that are in better condition will command a higher price.
The three-legged buffalo nickel happened because of an improper attempt to repair a damaged die, and several nickels were accidentally released for circulation before the mint inspected them. Collectors marvel over the fact that the front stump and hoof is still visible on the coin, but the leg is missing entirely.
Because these coins are valuable, many counterfeits have popped up over the years. On a genuine coin, the rear leg appears to have less metal, and it has a series of raised dots under the belly that do not appear on a normal coin.