

Hi
Can you help with this Britannia £2 coin that I found today. As you can see from the image, the front of the coin does not have the words 'two pounds' on it but does have the initials AD. The reverse of the coin, beneath the queens head, has the initials IRS (or possibly IRB) whilst the other Britannia coins have the initials JC.
There is no writing around the coin.
Can anyone help as to whether this is a fake coin or exactly what it is!?!
Thanks in anticipation.