I've got no idea, but Napoleon III was emperor of the 2nd empire of France between 1852 to 1870, that looks like silver, but it has the horse design from the British gold sovereign on the reverse, I'm gonna guess its a fantasy piece, but it could be a average circulation coin, I have no real numismatic knowledge of French coins sorry. Also, since the coin has been damaged, unless its a rare date, or a valuable piece of whatever it is, I wouldn't say its valuable.
It opens and has a chain on it no dates or maker mark i cant find anything like it amywhere and all smooth on the inside so strange
It is a terrible picture, but it appears to be something that looks like the reverse of a gold British half sovereign attcached to the obverse of a gold French 10 francs, but since it does not look like gold I assume it is simply a novelty watch chain fob or necklace pendant made from white metal imitations of these coins. PS looking at the coin size comparison in the other post it looks a bit bigger than I thought, similar to a a full sovereign and a 20 franc
