It depends on the value and when they were made. Lower value coins (10, 20, or 50 centavos) are currently made from stainless steel. Peso coins are bi-metallic (stainless steel/aluminum bronze). Circulating 20 and 50 peso coins are bi-metallic with a silver center.
You may consult the related links below for more information.
That number indicates the fineness or purity of the metal content. 900 means the coin is 90% of that metal.
silver on the outside/ small gold coin inside
Seems to be the metal coin content, of the coin.
The coin is 90% silver & 10% copper.
intrinsic value If a coin had value because of its metal content, you would refer to the "bullion value" or the "melt value" of the coin, as versus the "numismatic value" that a coin which was rare or in exceptional condition would have.
A 1921 Mexican 1 Peso coin contains 0.3856 troy ounces of silver.
Aluminum and Bronze
A US 5-cent coin is 75% copper and 25% nickel.
Intrinsic
It's 80% silver and 20% copper.
If it's a copy, it's not worth much of anything. At best, it's worth its metal content.
A slightly more sophisticated version of the Magician's Coin. Will the Mexican coin come out of the half dollar?