This K 98 Mauser is a classic WWII mil surp rifle chambered in 8mm mauser according to the 24" barrel. Bore is very good, I have not had time to fire this rifle. Marked 43 and DOU on the receiver.
DUO means according to the google machine - ""DOU" is an ordnance code that indicates that a Mauser K98 rifle was produced at Waffen Werke Brunn, A.G. Bystrica in Czechoslovakia. For example, a DOU 43 K98 means it was made in 1943."