Chester,
You didn't mention which action your rifle is built on. If it is a pre-98, small ring, cock-on-closing and with no gas shield on the bolt sleeve and if the stock is a straight grip, you could possibly have a Spanish Civil Guard rifle chambered in .308Win. If there is a strange looking tube, resembling a short gas tube under the barrel, you have a Spanish FR-7.
If it is a 98 type action, with a pistol grip and the "gas tube" under the barrel, it is a Spanish FR-8. I used to have one of these. It was chambered in .308Win. The "gas tube", is a compartment used for the cleaning tools and the cap on the end of the tube was for locking the bayonette.
I don't know the history of the Civil Guard or the FR-7, but, the FR-8 was simply a reworked Spanish 1943 Mauser. When Spain was converting over to semi-auto and full-auto firearms, the FR-8 came into being. It was roughly the same weight and length as the CETME and the .308Win (7.62x51) is virtually, not exactlly, the same as the .308 CETME. This seemed to make since to the Spanish military, get the troops used to firing a bolt action rifle that is roughly the same weight and length as a semi and full auto rifle. Being a bolt action, it could simulate firing the CETME in the semi-auto mode, the only difference being, the bolt action does not soak up the recoil like the auto, and that SOB had some pretty mean recoil. I am a big ol' boy, but it took only one round with that steel buttplate to get me to slip on a sissy pad. I have never had a problem with flinching, but it took a few rounds with the slip-on to get settled back down. I still hurt just thinking about that one, LOL.
I hope this helps you out in your search for which rifle you have.
Buddy