Click on the link I provided above, they are the authority on Spanish Mausers. I have a 7 X 57 cal. "un-marked 1916 Spanish Mauser I bought in 1967 for under $20 out of the Motgomery Ward's catalog. It seemed to be almost in new condition. Some folks think the Spanish-made Mauser's are inferior to the later '98's made in Germany, but I've shot countless hundreds of rounds through mine and it is very accurate and still tight as the day I got it.
Many of these guns started as 1893 Mausers and were re-arsenaled and converted at Oviedo, Spain around 1916. Many were converted to ".308" caliber, but be cautioned it's not .308 Winchester, but rather is closer to 7.62 NATO pressure. Chamber pressure for whatever round used should be kept in the range of 46,000 cup. Commercial 7 X 57 ammo available today will meet that pressure.
Here's a picture of mine: