Got this from CoinQuest.com The 'ley' in the inscriptions refers to purity of the precious metal. Ley 0.999 is (essentially) 100 percent pure gold or silver. But you might see a coin with a purity of 'ley 0.720' which means there are other metals in the coin and the precious metal is only 72 percent of the total weight. We are not quite finished with the Mexican twist! Sometimes weights are given in grams and not in troy ounces. You need the weight in troy ounces to compute coin value. There are 31.1 grams in a Troy ounce. A 100 pesos ($100) silver coin from 1978 bears the inscription: plata pura 20 gr ley 0.720 To figure value, we need the actual silver weight. There are 20 grams of pure silver in the coin, so: 20 grams / 31.1 = 0.643 troy ounces of silver The 'ley' purity is only 0.720, so other metals are mixed with the silver, but the pure silver weight is 20 grams or 0.643 Troy ounces. Diddnt realise fishball had already responded
It's more than just "amount" it actually means "legal amount" Therefore de ley oro - means more along the lines of "containing the legal amount of gold" or de ley plata - means "contains the legal amount of silver". malachii
