I am going to try and take it to a gunsmith to test the hardening. I have looked at the bolt/receiver all over with a penlight and magnifying glass and the only markings are the SN, emblems, and swastika on the floorplate. There is a 7 that seems "random" on the receiver. I have thought about taking off the floorplate to see if anything under there. But, so far I am unable to find any "z" or dates. I will update when I find anything of interest out. Thanks to all for the imput. Great site. Look forward to being a member.