I purchased the elements of this lovely set separately but they match as well as if they were made for each other. The screw back earrings are signed “Taxco Mex Sterling 925” in a circle around “P.A.”. The brooch is signed "ASC Sterling" inside a triangle formed by "Cuermor Ley 925 Hecho en Mex", indicating that it was made in Cuernavaca in the Mexican State of Morelos. There is no eagle mark on any of the pieces, indicating that they were likely made before 1948, based on information in Bille Hougart's “The Little Book of Mexican Silver Trade and Hallmarks”.
A brooch similar to this one is featured on page 136 of Karen Edeen's "Vintage Jewelry".
Abalone is the "pearly" interior shell-lining of the mollusk of the same name that can be used for inlay and other decorative purposes. (It is referred to as Paua in New Zealand.)
Both brooch and earrings feature raised curved abalone with sterling leaf veins and stems. The green and purple glimmering iridescent swirls of the abalone are a lovely complement to the silver’s warm patina. The earrings measure 1 ½ by ¾ inches (3.8 by 1.9 cm) and the brooch measures 2 3/8 by 1 3/8 inches (6 by 3.5 cm).
The brooch has several dimples in the silver on its underside that appear to me to be original to the piece. The set is otherwise is excellent condition.