I recently picked up this Mauser but am unclear on exactly what we have here.
When I first saw it online, my first impression was that it was very Schuler like. It was advertised as a Stogos in an unknown chambering with a +/- .44" bore. I guess the seller never bothered to take it out of the wood.
I figured it had to be either 11.2X72mm or 11.2X60mm, either of which would be a great addition to the stable and a great companion to my .500 Schuler. I don't have Speed's book yet, so bear with me.

Well, much of the mystery cleared up once the proofs and marks under the wood were revealed.
10.8mm x 72 is stamped on the barrel - this is the bore dia. for a 11.2mm groove barrel right?

Looks like a build date of May 1926. 6013 and Stogos on both the bottom metal and the barrel.
One very intersting feature is the brass spacer between the action and the bottom metal to allow for a greater magazine capacity. I can see that this would be a much less expensive alternative in time and material to a drop magazine such as my .500 has.

Can anyone here shed more light on this rifle?

Looking inside the magazine.