You are biddding on a used rifle for a small ring mauser, such as the Swedish 96, the Peruvian 1909 or the famous G33/40 and others. The barrel has the caliber 8mm Mauser, or 8 x 57mm. The exact caliber 7.91mm is stamped on the barrel. The base of the rear sight is still there, the rest of the sight is missing. Bore is fair, needs a good cleaning. Good luck bidding!