Thanks everyone for all the info, really appreciate all for you taking the time provide all this valuable input. I am adding some pics of the serial#'s as there was a few reference to the serial#.

To be fair to my smith, he is not a Mauser expert and was strictly making the suggestion from a hunting convenience point of view as it will be quite difficult to get .318 bore ammo(he assumed a European caliber) . I am sure he must have thought that this is a military converted sporter.

I am just going to add a Mauser butt plate to the rifle and leave it alone. I will also try to source some .318 ammo. Will also try to get chamber cast.