Both the 156,14 and 7,85( Germans used a"," where we use".") designate the caliber. The 156.14 equates to 7.87mm,and the 7.85 is also in mm, both as the bore diameter-not groove or bullet diameter. Now, this is pretty interesting since the 156.14 is under the 1891 law, which was changed in 1911(effective date 1912). What makes you believe it was made in 1912? Without other photos,it is not clear whether this is a sporting or military rifle. The photo does show a military type rear sight. This is the interesting part, the first military Mod 98s were chambered for 8x57I. In 1903 the I cartridge(318 RN bullet) was changed to the IS cartridge(323 Spitzer bullet), but the adoption was held until 1905.The time between these dates was used to manufacture a sufficient stock of ammunition and inspect ,as well as mark, all rifles in the inventory for use of the new cartridge(IS).Is this why the caliber is marked twice? is this why it has an "S" marked on it or is this for something else? Are there any marks on the right hand side of the buttstock?(it has been learned that some sporting rifles were used as sniper rifles during WW1 and underwent a similar inspection). Are there clawmount bases(or have any been removed)on the rifle,or any type scope mounts?( all sporting rifles used for sniping were equiped with scopes).Our member Axel is working up a study of 8mm cartridges,and hopefully he will offer his advice on this rifle.
The middle photo is the clearest and it sure looks like a "6" to me ,even after a relook.From the photo it looks like a very nice "straight up"Mauser Oberndorf sporter.Without the stock markings,scope mounts,or Imperial acceptance mark; it is not one of the sniper rifles. If a fired but unsized case will accept a .323 bullet,it would be OK to shoot 8x57IS. If the barrel slugs .323", it was made as 8x57IS. I still wonder what Axel thinks.
Slug it if you like, but the single S marking is already there. It is, of course, 156.14 stamped and has the 7.85mm marking also.
I once saw these same markings (noted above) on a K98k (WWII vintage) that had been, for whatever unknown reasons, reproofed commercially. A military Mauser would not have had the Crown U,B,G or N. A military accepted Mauser would only have had the Imperial eagle proof indicating it had passed the proofing process. Later during the Weimar period a "stick" eagle would have replaced the Imperial eagle. Still later, post January 15,1940, the eagle would be a 'straight' winged eagle (horizonal feathers) with a swastika under it. Regards, JIM