Possible this was made while she designed at Los Castillo's prior to 1948. Notice besides not being signed by the maker it's only marked Sterling Mexico, there are no Eagle marks. I've studied brooches by Margo de Taxco that are signed in this design and the only difference is the length of the mices noses and the curl of the tails on the attached mice in the front of the coach on chain. Everything else is the same including the size. Remarkable brooch with wheels that spin and move when worn as well as the chained mice that displays beautifully and sure catch admiring eyes and comments. Guaranteed sterling silver. The coach measures 2-3/8" wide and 1-1/2" tall. The attached mice are 1-3/8" wide x 3/4" tall and weighs 14.7 grams. Overall lovely patina on this amazing piece!