1930's clear rhinestone clamshell shoe buckles. Measures approximately 1 1/2" x 1 1/2". These are not marked but they are an exact match to the dress clips on our site that are marked WMCA ( White Metal Casters Association) Go to item j1020723. 
 
See "Collecting Rhinestone & Colored Jewelry - 3rd Edition" by Maryanne Dolan for wonderful examples of shoe buckles. This book also includes a comprehensive section on Designers Marks.