Mattle
The number on your stock may represent an arsenal/inventory number placed there by previous owner(s). I have a 1910 with the same thing, and at least one Original Mauser that has the Safari companys inventory number stamped in the same place. Sometimes individuals initials were included.
It may even be a retailers inventory number, but never in my experience are these " stock" numbers related to the makers serial numbers....hope this helps.

Eric