NICE RIFLE.. Worth twice that Id say.. yes its early enough to have an unnumbered bolt.. bolt numbering started later. also looks to have a KKW marked muzzle cover !!! not common to have that included.
The same guy came.in the next day with 2 22 conversation. One was a single.shot.erma and the second was a later repeater erma24 that one of the lugs that goes in reciever lugs is broken off. I didnt have a single shot so im keeping that one for sure. Neither of them were in the boxes and the repeater was just the complete barreled action but he was fair price so i bought them both. So now everything resides with my only other German 22.
If you dont get a response, you might try a length of 3/16 rod with those measurements marked on the rod and insert it in the hole. The rod should go down and be stopped by the retainer. See which length you deem more appropriate(allow about a 1/4” to screw into the retainer) To get you around the middle of the front sight. I haven’t tried this but I think it will work.
As Far as I know,going by my own rifles, BSW, Gustloff and Walther all used the shorter of the rods. I do not have an early Mauser KKW, but the late ones with the D.F. after the serial number used the long rod.
There is a guy on ebay and Gunbroker selling repro rods for the KKW