Some photos of a recently acquired Mauser.

It is a single square bridge TypeB made in 1904.
The scope mounts are Rigby style which use a single rear facing hook for the rear and a notched pin for the front.
I believe that this is actually an early Mauser system which was adopted by Rigby for their house style scope mounting.
The rear sight is a 1000m tangent with windage adjustment which was an optional upgrade to the factory standard TypeB. This sight is standard on the Special Range Rifles.

One non-original feature is the floorplate and release.
I am thinking that the military style button release was changed out for a lever style and a different floorplate was utilized as the floorplate on the rifle is the only part with a non-matching number.
The grip cap is horn and I think the stock is from another Mauser as there is a filled gap at the front of the bottom metal ahead of the front action screw. Hardly noticeable though.

Perhaps the most unusual thing about this rifle is that it is chambered in the 8X51 Mauser cartridge.
The 8X51 was offered in the Kurz actioned rifles but I haven't seen that chambering in a standard length action. It had some popularity before WW1 so I suppose a buyer could have requested such a rifle.
Of course, it was sold as an 8X60 which I knew would not have been original for a 1904 rifle and assumed that it could have been rechambered to 8X60 from 8X57.
The rifle has a .311" bore measured with pin gauges and has four groove rifling. The bore condition is excellent.

This rifle is set up almost identically to the unique SSB large ring Kurz rifle on pages 115-117 of John Speed's wonderful Mauser book.
Interestingly, the B U proofs on the action are below the wood line and there is no stamping of the chambering on the rifle!