How much is a nickel that is blank on the obverse worth?

Answer 1

This could happen if two blank planchets got into the press together, causing one to get stamped with only the heads side, and the other to get stamped with only the tails side. This is a relatively rare error, and could be worth $50 to $100 or more. This could also be a normal nickel that somebody has altered. If it weighs significantly less than 5 grams, then I would say that it has been altered and has no added value. You can check out the ANACS website to see if they will be attending any upcoming coin shows in your area, where you can take your coin and get a free professional appraisal : http://www.anacs.com/shows.html

Answer 2

If the coin weighs less than a standard nickel, someone with too much time on their hands smoothed off the back. If so, it would be considered a damaged coin worth only face value. If it's the same weight (5.00 gm) as a normal nickel, there is a slight possibility it's a minting error that resulted when two blanks got stuck in the coin press at the same time. One blank would then be struck with the front image and the other with the back image. You'd have to take it to a dealer who specializes in error coins and have it examined first-hand.