This belongs to a friend of mine. I don't have a weight or diameter, but could get both of necessary. The coin was about the same diameter as a US Nickel.
O.K. here is what I have It is a Carinus tetradrachm/Roman provincial Egypt/first half 283 -spring 285 AD. Material made from is billon.I have the same coin That is why I have this info.If you google Carinus tetradrachm you will find it and a lot of others from same era.Not worth a lot just don't clean it, lessens it's value.