Nice coin, worth probably around a dollar or two. It says here https://en.numista.com/catalogue/pieces778.html that it is made out of copper-nickel.
If I recall correctly, those were minted by the boatload. Lots of those to be found in the 5-for-a-dollar bucket at coin shops and shows. By the way, yours is a 58, not 57. All (most?) Spanish coins from that era had 1957 on the obverse, but the actual year of issue is contained within the tiny star on the reverse. I believe that was continued into the mid-70s, maybe longer. Edit: My apology, Mr. Pie. I failed to see on first reading that you noted the 58 star.
I love world coins best. If you keep them maybe a younger family member may appreciate them in the future.
PTAS is short for Pesetas. That's how the word Quarter translates into spanish.. 1 Quarter is Una Peseta