I guarantee it's authentic or your credits back. These were bought in a group uncleaned and I am listing them one by one. I removed the crud and cleaned it up myself that is how I know it authentic by removing the 1000+ years of dirt and crud. Now it's very presentable and identifiable.
Also, another way to tell if it is a real ancient coin is by looking for damage and wear. I mean if the coin is undamaged and has no wear just tarnish well then you should be concerned. This one should be obviously authentic.