Hi, welcome to the forum. You expressed an interest in the paper decal on your pin/brooch.
Due to certain design or composition features, many pieces could not be safely stamped with the eagle mark. This could be an item like your abalone pin/brooch. In instances where it could not be safely stamped, the eagle mark was imbedded in a small metal seal attached by a wire loop to a silver piece before sale. Although some of these metal seals are still attached, most were removed after purchase. Paper decals with the eagle mark were also affixed to some objects. [Hougart]
Eagle 1 represents the Federal District of Mexico City. However, finding items stamped for Mexico City made by a Taxco-based artist, or one by a Mexico City firm stamped for Taxco, is not uncommon. [Hougart] The eagle stamp system was officially abandoned by the Mexican government by about 1980. Since about 1980, Mexican silver has been marked using a registration system combining letters with numbers, i.e. TP-54.
My references do not identify the maker, but I do see the Taxco mark. It was made prior to ~1979. Someone with more experience with jewelry might be able to tell you about the age of your pin/brooch by the type of clasp on it.
http://www.925-1000.com/mexican_marks.html
Best wishes, TD
