|Above is a sampling of Mexican silver purity marks ranging from ca.1900 to the 1970's. The "Mexico Silver" or "Silver Made in Mexico" marks are seen on pieces from the 1920's through mid 1940's, their silver standard varies, but is commonly above .925 purity.
The following number marks indicate silver purity in a percentage of 1000ths. The intaglio "900" mark is found on work dating from the turn of the century until the 1920's. The intaglio marks "980, 960, 940 & 925" are usually from the mid 1930's to the mid 1940's. The incuse mark "970" was the favorite standard of Antonio Pineda. Most work from ca.1950 onwards is stamped "Sterling" or with an incuse "925" stamp.
The "Eagle" form marks to the right were instituted by the Mexican government in 1948. The first example (delineated) was used until ca.1955, the second example (silhouetted) until the late 1960's or early 1970's. The number on the eagle's chest indicates either the city of assay or an individual maker. (eg. Eagle stamp #1 was for Mexico City, stamp #3 was for Taxco, stamp #16 was registered to Margot). There are many variations and exceptions, the above info just provides a general framework to what was a relatively loose system.
About 1979, the eagle system was put to rest and replaced by a new letter/number mark to indicate the silversmith and guarantee sterling standard.
The first letter indicates location, and there are few in use, those most commonly seen are: T, M, G & C
In this example the T is for Taxco - others are M for Mexico City, G is probably Guadalajara and C most likely Cuernavaca.
The second letter indicates the first initial of the last name of the silversmith, in our example it is C.
The number indicates that he is the 45th smith, with a name beginning with C, to register a mark in his city's assay office.
So... this example, TC - 45, tells us that the item on which it is stamped, was made by a smith with initial C sometime after 1979 in the city of Taxco. Generally that is all that can be derived from these marks, Unfortunately, there is no list that matches the letters and numbers to silversmith's names and there are probably less than 15 of these identified. Our example happens to be the mark of Antonio Castillo, one of the founders of Los Castillo and it is one of the very few known.
Individual vintage Maker's Marks are illustrated below.