English stocked German guns are not common. In my experience the German guns tend to have pistol grips and cheekpieces, but straight grip English style stocks are not unheard of and definitely more desirable to those who do not like the cheek piece stock. It is quite possible it is a restock, but that is really not that important in a shooter.
One thing I forgot to mention is checking on the smoothness of the cocking action (thus could detect leaf spring issue - which unlikely are still possible) to do this one barrel at a time you will need a snap cap. Fire on one barrel, leaving the other cocked open the action and gently recock the fired side. If one side is appreciably different it might indicate an issue.
