Tikka / Ithaca 12-70 .222 Rem Over & Under ??

Hey Guys:

Here are a few pics of the Tikka/Ithaca I recently got from my grandfather. It appears to have an Xtra full choke tube in it. It has never been out. I have been looking for information on this gun. All I know is that it IS an awesome turkey gun, and the accuracy is amazing. I was told that the choke may be something that was done to the gun. Granddad said he bought it new, and never had any work done to it. Does anyone know how many of these were made? Any other caliber setups? I would love to get another. I have only seen one similar to it before, but it was a Savage.
Thanks Guys