What is a Mexican 20 dollar piece?

Answer 1

Mexican currency is denominated in pesos rather than dollars, but they use the $ sign to indicate pesos, so it causes a lot of confusion.

You'll need to post a new question with your coin's date and a description of the image on it. The date is very important because Mexico changed the value of its currency in 1992-93. "Nuevo pesos" (new pesos) were issued to replace old ones at a 1-to-1000 exchange rate. That means if you have a coin worth 20 nuevo pesos, it would exchange for about two U.S. dollars. However, if it's old pesos, it would be worth only one-one thousandth as much - i.e. just two-tenths of a cent.