1937/1940 Nickel In One

If that is both sides of the same coin then I would say it's a majician's coin. They drill out one side leaving the edge on put a new center in.

Try putting it in to a glass and swishing it around in the bottom of the glass allowing it to bounce around off the sides. Sometimes this will separate the 2 halves.

Sometimes a seam wont show on the edge, one side is milled out leaving the edge intact like a bowl, then a similar milled top piece is dropped in, these are known as a spy/smugglers coin as they are usually hollow inside to hold a note or micrfilm (cold war era). I have a 1972 Kennedy half that comes apart but when snapped together there is almost no discernable difference from a normal half dollar, the inside lid has a Mexican centavo coin on the underside of the lid so I can make multiple coins appear and disappear. Very cool novelty, but not a mint made coin.

The reverse and obverse coining dies are different sized on the attachment end of the press to keep two of the same sides from being placed into the coining press paired together, think round and square pegs. There is no physical way to mate a pair of same side dies in a coin press.

edit; found a link showing the coin and the trick I have, http://www.howcast.com/videos/35563...a-Coin-Trick