Aha-- the 1948 cutoff date for the linear stamp on the Los Castillo page was making me worried, since its timeframe didn't overlap with the "Hecho en Mexico" stamp. So it is sterling, dating c. 1952-1955... wow. Thank you for the confirmation!
I have what appears to be an early Los Castillo parrot pin, but the markings don't quite match up to the ones listed here : the "Los Castillos" name is in a single straight line instead of a circle, and there's no mention of Taxco. I believe the number on the eagle is "15", but t...