1-ounce silver coin, called the Libertad (Liberty)

Mexico Mulls Silver Lining Against Currency Crash
hm no face value, tied to value of the metal. How do you declare it?

An influential Mexican businessman wants to reintroduce silver coins as legal currency -- as in Mexico's 16th century heyday -- and, far-fetched as it may sound, the idea is winning support. [...]
The 1-ounce silver coin, called the Libertad (Liberty), would have no nominal value engraved upon it, and would circulate alongside the conventional peso currency. Its worth would be stated daily in a central bank quote.

Update:
Here is Hugo's essay advocating this:
HOW TO INTRODUCE THE ONE OUNCE SILVER "LIBERTAD" COIN
INTO CIRCULATION IN MEXICO

Though not the central objective of monetizing silver, undoubtedly the coinage of large amounts of "Libertad" coins, which would be eagerly accepted by all Mexicans, would impact upon the price of silver, and be of great benefit to Mexican mining, which is providing large amounts of silver to the world markets, at ridiculously low prices, to the detriment of Mexican mining and the Mexican economy, which is hungry for a mass means of savings in a medium which will guarantee the conservation of value through the years.

Contains 1 troy oz. of pure (999 fine) silver. Brilliant Uncirculated – just as we received it from the Mexico City Mint. A graceful Angel is depicted; in the background are “Lovers’ Peaks” – two volcanoes that memorialize a prince and princess from different Indian tribes who fell in love, eloped and were eventually exiled. Reverse features the different versions of the national seal of Mexico – an eagle with a snake in its beak, standing on a cactus.