For your consideration is this large Mexican bird pin. Done is a puffed style with dimension. Mark was hard to read until I found it laid out exactly the same way in my book - Coro Mex Silver in a circle. It has tested as sterling silver and the mark of Silver was used prior to 1945 on sterling silver. It has a old c clasp.
This is large measuring 3 and 5/8 inches by 2 and 1/8 inches across the widest points!!
Excellent functioning condition other than a very very uneven old patina. Hole in back is part of the making and you always see these in puffed pieces.