I have a 1939 kriegsmarine BSW but the barreled action is sadly a BNZ 4
But the serial numbers on the BSW are 2369 and the takedown pin on the back is marked O.21205 with waffenamt eagle 4.
Lucky for me, my bands, furniture, bayonet lug, buttplate, and a couple of other items all match For the full stock set.
Mauser lover told me a couple months back that it is a captured k98 because On the buttplate the 2369 was scratched through and a -68277- was stamped over it. I had forgotten which country he stated does this but he said they only restamped a couple of parts and that was it. Besides that, none of the rifle had been refinished, no other markings were removed. And I recently disassembled the rifle to inspect and clean some dirt and dust from the cracks and edges.