If it is chambered for the .30/'06, it is obviously not an original GEW. 98, they were 8X57mm. It must have been rebarreled. If so, it is surprising the barrel is not marked ".30/06". Is it posssible that it is the original 8mm barrel, rechambered for the '06 case, and therefore an 8mm/'06?? If so, this is an excellent caliber, although one which requires one to handload for it..........

Keep yore powder dry!!