The Board was kind enough to offer some input a while ago on an old and odd roller I acquired last year:

(You need to Login or Register to view media files and links)

For what it's worth, I have been searching further since and I believe there was a number of rifles put together in Germany for Mexican interests during the Mexican Revolution (1910 through 1920).  Sure enough, on a closer look my rifle has German proofs in a configuration I understand would date after 1912.  The grinding was done on the gun before I got it, and I think may have been removal of prior proof stamping from the barrels first life, but have no idea why the area didn't discolor over time.  If I am reading the proof stamp right the proof is for a 9 gram (about 140 grain) steel jacketed bullet and nitro powder.  Proofed by the Germans for the 7x57 with nitro powder maybe the gun might be shoot-able with very modest loadings after all??      

Bailey, you had asked earlier if my rifle barrels were marked similarly to yours. All three were so marked, one has not been ground over in any way. All the markings shown in your photo are present. The caliber is clearly marked.  Additionally in the area your rifle barrel is ground mine has a serial number. The mark under the crown below the lower crown etc is a U.  The second rifle is ground much the same as yours to remove the serial number.

Looks like I got my answers.  Thanks to all. 

(You need to Login or Register to view media files and links)