the difference seems not to be so much that it realy makes the difference. I can only assume that something was changed sometimes.
we will wait for kudue as being the man for such questions. its the long pentecost weekend so he is maybe busy and dont see it before tuesday.

I wonder myself about the stamp on your collath mauser
http://forums.nitroexpress.com/showflat.php?Cat=0&Number=208805&an=0&page=0#Post208805

"I have a question about the proof on the side of the receiver.
You can see in the photo that the rifle was originally proofed
at 2.67 gG.B.P. but later reproofed at 2.45 gG.B.P."

can only imagine that the 2,67 was an error when made and they stamp the 2,45 over this.