Bnz is the factory code for Steyr Daimler Puch from 1941 to 1945. The 41 beneath it is the year of production, 1941. The serial number 5717i is the serial number of the rifle and all parts would have been numbered to that serial number when it left the factory. The bolt is mismatched (7558h) and additionally has a mismatched bolt shroud and safety (3121). A stock for an original bnz 41 would have 3 acceptance stamps on the right side by the bolt takedown disc, an eagle above H, L, or M and two WaA623 stamps. The stock's serial number should be on the bottom of the stock towards the buttplate if it's original, otherwise they're usually numbered inside in the barrel channel (same for the handguard). Like bnz41john mentioned, get more pictures of all of the markings. Both barrel bands and bayonet lug are serialized in addition to most of the rear sight parts, floorplate, triggerguard, action screws, etc.
