Looks like Maurice Tiberius but I am unaware of any with that reverse type. Edit, this appears to be a similar reverse...Justin I, 5 nummi with large christogram.
Is the coin bronze? I'm a little concerned about the spotty black patina. It makes me wonder if someone was deliberately trying to cover up something. If the coin was supposed to be silver, I'd say it was a fourrée. But that's just an impression, and it's probably meaningless. I really can't tell much just from the photo.
