My first guess was an item made to look real enough that someone would buy it...but I know very little about ancients.
This is a fantasy coin of Constantine I, obverse is of a roman coin and the reverse is of a judean coin. The coin was never used in ancient times and isn't that old. There's more info on it here: http://www.constantinethegreatcoins.com/fantasycoin/ Still an interesting coin though, I would keep it as a 'fun coin'
Thanks for the link AA. It's impossible to even call it a fake, because no such coin ever existed. The reverse never existed, the portrait style is all wrong, and the lettering doesn't even attempt to imitate Roman style. The only person who could be fooled by such a thing is someone who had never seen a Roman coin.