Mexico has a long history of producing gold coins, but the most commonly collected ones are the gold Onza, the gold Libertad and the gold 50 Pesos coins.
Of these coins, the 50 Pesos coin is the most easily obtainable, as it was minted in great numbers – over a million were produced in each of the years 1945 and 1946 alone. They were first issued in the 1920s, and were one of the few ways of owning gold bullion coins before Krugerrands came on the market. They were last issued with a date of 1947, and many restrikes have been produced of that date since. As with most Mexican coins, the obverse shows the National Arms or coat of arms of Mexico (an eagle on a cactus, eating a snake), while the reverse shows Winged Victory, the face value and the weight. The 50 pesos coins are 0.900 gold and weigh 41.67g (1.34oz). Note that this is 1.21oz actual gold weight, and bear that in mind when buying them.
For a larger image of a 50 pesos coin and some tips about spotting fakes, see this Kitco page.
The obverse and reverse sides of the Mexican 50 pesos gold coin
The gold Onzas and Libertads are bullion coins and carry no face value. They are similar coins, in that they both feature the national arms of Mexico on one side, and winged Victory on the other. In fact, both are referred to as Onzas in the main gold coin reference book (The Standard Catalog of Gold Coins). The main difference is that the Onzas, which were produced in the 1980s, are 0.900 gold, with a total weight of 34.5g . The Libertads, which were produced from 1991 onwards, are 0.999 gold and weigh 31.1g. If you are buying these coins as gold bullion, there is no difference between them.
Both sides of the Mexican Libertad, also called the ONZA
Mexican gold coins for sale
More information about Mexican gold coins
Mintage numbers for 1921 to 1947 for the 50 pesos coin
Differences between the Onza and the Libertad, for collectors
Bullion gold coin comparison chart