I would say its a 8x60 (I bore so not 8x60S)
you can load it with a 8x57IS die set. brass can be made by using 30 06 cases or buy PRVI 8x60S cases.

what I found on your pics was this

H K remind me allways on Heinrich Krieghoff/Suhl, well the sign between was not looking like an anchor but the lower part was grind off.
take a look at this Krieghoff Parabellum

http://jamesdjulia.com/item/3094-358/

I never notice bevor the Krieghoff sign was a combination of an anchor with a sword.
not doubt this Mauser rifle was made by Krieghoff in Suhl ... but for Bernal Arms?

google is your friend:
https://www.proxibid.com/aspr/H-Krieghof...sp?lid=20079553
H. Krieghoff for Bernal Arms Co. Best Quality Model boxlock ejector SxS ha

"H. Krieghoff for Bernal Arms Co. Best Quality Model boxlock ejector SxS hammerless shotgun, 28 gauge, full/full choked, 30” blued barrels, finely engraved receiver with four gold game scenes, raised floral engraving on recoil shields, finely engraved breech end of barrels, deluxe checkered wood stocks with beavertail fore end, beautifully flame grained butt stock with Pachmayr hard rubber butt pad, single Miller trigger, 14-1/2” length of pull to end of butt pad, #14106 in overall fine condition showing the majority of its blue finish on the barrels, fine bores, crisp actions, gold barrel address “BERNAL ARMS HIGHEST QUALITY”; fine wood stocks, exceptional engraving; even the safety lever on the upper tang is finely checkered. (Modern). Est.: $10,000-$20,000."

so Krieghoff had a business relationship with Bernal Arms Co. in the united states, wherever this firm was.