Sap, I haven't got a scale of any sort to weigh the coins upon. However, I can answer that the line is a piece of cardboard from the 2x2, probably the same one. >.> I scan these on my flatbed scanner in multiples, and just don't notice those little things until well after I've already posted them up ><
I'm aware that many Asian coins are coming up counterfeit, but when I get them like this, I worry a little less. The coin shop where I deal has people in selling constantly. This was in a lot that they bought today, a mass of old silver Mexican rounds, plus a very few old World silver coins. The things have probably been hoarded for half a dozen decades.