Found a Mauser, Need Help with Markings, and What Mauser it is?

[vintage hunter]

If you make the firearm yourself, it doesn't have to have a serial number

Your right, but from what I've read the ATF strongly recommends it does so it can be identified if it's lost or stolen.

you decide to transfer it.

The laws concerning an unlicensed person manufacturing a firearm for personal use are quite clear but they get really murky when it comes to legally transferring one. Only conclusion I've been able to draw is it would be wise to have the ATF's blessing(in writing) before the transfer takes place.