I learned how to make a box like this in a college class project in metal smithing. The task was to create an enameled "stone" and set it in a copper box with copper prongs. For this piece I textured the copper and then enameled it with various transparent enamels melting a few glass beads on top for texture. The box was created with copper strips that were measured out and soldered. The prongs were created and then the "stone" was set with the prongs going over to hold it in place.
I enjoy making box pendants now.
Dimensions: 1 inch square pendant on an18 " sterling silver snake chain