Handy Mike,
That fits in with several of the arsenal rebuilt 1912 rifles from Chilie, although the 308 is not something that I'm familiar with, thus the reason for the original or customized question above.
According to the latest edition of "Mauser, Military Rifles of the World," given your NATO stamp on the ring, there should also be a "61" following the NATO on the rifle's reciever ring. That apparently changed its nomenclature to a "Modelo 1912/61. Some had shorter barrels installed when converted to 7.62 NATO, but mine has the original barrel length (28.75") and of course the 7.62 N marking on the bridge.
I was TDY in Chilie a few years ago and while I've seen Mausers in other South American countries, I didn't see one in Chile, even though I looked pretty hard.