Interesting, I suspect you are right. With such a low percentage of silver, it's basically a clad coin for all intents and purposes
Honestly Mexico has some of the best designs of any country in the 20th century, period. They're not very expensive either, and probably one of the more affordable sets to put together!
This is basically a copper coin with a silver plating. When new, they look nice, toning or not, when worn they look like crap.
This coin is 72% silver, denoted by the 0.720 just above the eagle. Silver Mexican coins often (perhaps not always) show the % silver this way.
If you're ever in Jacksonville, Florida, the name of the store is Edgewood Coin Company. They mostly specialize in American coinage and bullion. However, they do offer a large variety of foreign coins and currency. Prices are reasonable on their foreign coins, particularly any foreign junk silver when they do have it, but I feel that most of their American coins are overpriced.